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Lecture: Answering MG Questions and Diagnostic Method
- 1. Master Gardener Training: Answering Questions & Plant Problem Diagnostics Brooke Edmunds, Ph.D. OSU Extension, Community Horticulture brooke.edmunds@oregonstate.edu
- 2. Resource List Sustainable Gardening: Chapter 16 Further reading: – PNW Disease Management Handbook • http://pnwhandbooks.org/plantdisease/diagnosis- and-testing/disease-diagnosis-and-control – Factsheet: 20 Questions on Plant Diagnosis – http://plant-clinic.bpp.oregonstate.edu/year
- 3. Diagnosing Home Gardener problems and making recommendations A day in the life… Of an OSU Master Gardener
- 4. The Desk: Homeowner Home and Garden advice MG program began as a way to meet demand for this information Restricted to calls from non-commercial sources Provide diagnosis and advice in the office, by phone or email
- 5. Two big advantages… 1. It’s free! 2. Talk to an actual person
- 6. Requests are either… Phone calls E-mail Visits to the office
- 7. Requests for information are usually: 1. Plant identification Ornamentals Weeds Apple/pear/plum variety 2. Insect Identification 3. Pests in the home ants (carpenter, sugar) termites pests of stored products spiders!
- 8. Lawns Pruning propagation 4. Critter problems Deer control voles moles gophers 6. Plant problems (including lawns) Cultural Disease Insect pest Herbicide damage 5. Requests for cultural information Tree fruit Small fruit Ornamentals
- 9. Difficulties: 1. Client may only tell you so much 2. You cannot visit
- 10. A simple intake form assists with problem solving: OSU Extension Master Gardener Client Information Form – Plant Problem Use this form to take down client information and to refer cases to the next MG shift. Name of Intake Person___________________________ Date____________AM____PM____ Client Name_____________________________________ Daytime Phone_______________ Mailing Address______________________________________________________________ (Street Address) (City) (Zip) Email Address______________________________________________________________ __ Provide information based on “Questions to Ask Clients” form in binder. (Use the back of this form if more space is needed) Type of Plant Tree__ Shrub__ Vine__ Herbaceous__ Evergreen__ Dedicuous__ Houseplant__ Name of plant, if known_______________________________________________________________________ Where is it growing? Indoors___ Outdoors___ Potted___ In ground___ Greenhouse___ In water___ Exposure Full sun__ Part sun/Part shade__ Full shade__ Soil Sandy__ Loam__ Clay__ Where is the problem on the plant?____________________________________________________________ How many of this type of plant do you have?_____ How many have this problem?______ Are any insects or mites present? Yes__ No__ If yes, how many?________________________ Fertilizer? Yes__ No__ If yes, what?_________________________________Applied when?_______________ Irrigation? Drip__ Soaker Hose__ Sprinkler__ Hand__ How often?_______________ Duration____________ Transplanted? Yes__ No__ If yes, when?____________________________ Sample Provided?__________ Describe damage/problem____________________________________________________________________ ___________________________________________________________________________________________ ___________________________________________________________________________________________ ___________________________________________________________________________________________ ___________________________________________________________________________________________ Any treatments or remedies applied? Yes__ No__ If yes, what?______________________________________ When?_______________________Result?_________________________________________________________ Answer & Client Notification MGs addressing this question: 1___2___3___ If question is not answered after 3 MGs have attempted to answer, pass question on to Home Horticulture Agent. Diagnosis or identification Recommendation Source(s) of information Client notified by ___________________Date________________Via phone_____Via mail____Via email_____ After notification: 1) Record completion in Daily Log. 2) Save Sample. 3) Place form in Archives loose-leaf. 2) The clues 3) Your diagnosis & how to solve 1) The client
- 11. The resources we use are… Books Web-based -add site:.edu to your search
- 12. What kind of information do we give out? Verbal: Information over the phone or in person OSU publications • Printed from the web • Hard copies from office files http://extension.oregonstate.edu/catalog/
- 13. Inquiries to avoid: 1. Commercial operations… • Size of operation • Is product being sold? Refer these to your MG coordinator or commercial Extension agent!
- 14. Others to refer to MG Coordinator… 2. Human health issues • Poisonous plants 3. Legal disputes 4. Mushroom ID
- 15. House calls Full soil tests or water tests Things we do not do… EM 8677: Laboratories serving Oregon EC 628: Soil sampling for home gardens and small acreages
- 16. Handling a frustrating case • Step back from the sample and look at the big picture • Request more information: – A fresh sample – A bigger sample – Photos • More than one problem may be involved • Symptoms can be affected by: – Environment – Plant genetics – Physiology – The pathogen or degree of abiotic stress Definitive diagnosis is not always possible
- 17. Other MG’s MG Coordinator Crop Specialist You don’t have to do it all by yourself!
- 18. Insects (and spiders): • Insect ID clinic • No charge per sample Plant Disease: • Plant Disease Clinic-Melodie Putnam • $75 charge per sample Plant ID: • OSU Herbarium-Dr. Richard Halse • No charge per sample We also can use other faculty and clinics…
- 19. Recording inquiries Tallied for OSU year-end report
- 20. Plant Identification Myrtlewood, Umbellularia californica
- 21. Most of samples brought in are from gardens • People with new gardens • Seedling plants that appear • Weed samples-how to eliminate! ID not possible? Leave for me!
- 22. OSU plant ID website: http://oregonstate.edu/dept/ldplants/ Lonicera pileata
- 23. You should have: More than one leaf! Flowers or fruit best! Chokecherry (Prunus virginiana) Strawberry Tree (Arbutus unedo)
- 24. Some samples are more common than others Catalpa Paulownia
- 25. Weed identification Japanese knotweed Same sample required Announcements in paper of “noxious weeds” bring enquiries
- 26. Mushroom ID-a special case
- 27. Most people want to know: • Is the mushroom edible/poisonous • How to eradicate from lawn/garden Rake mushrooms up Slime mold (Fuligo sp.) Aleria aurantia
- 28. Oregon mycological society http://www.wildmushrooms.org/ Leave ID questions for me… • I take digital pics • Email to campus Willamette Valley Mushroom Society http://mushroom.byethost12.com/
- 29. Moss and lichen
- 30. Moss and Lichens are not pathogenic
- 32. Moss in the lawn FS 55: Controlling moss in lawns Scholars Archive http://ir.library.oregonstate.edu/xmlui/
- 33. Insect and Spider ID Scale insects on Wisteria
- 34. Information to get: • Host plant? (or if in soil…) • When was it noticed? • Damage? (if there is any) • Control measures used? Garden insect problems Rose aphids
- 35. Aphids on Plum PNW Insect Management Handbook: http://pnwhandbooks.org/insect/
- 37. Other emerging pest insects… Brown marmorated stink bug (Halyomorpha halys) Azalea lace bug (Stephanitis pyrioides)
- 38. Household pests Human health: • Cockroaches • Fleas Structural: • Termites • Carpenter ants Stored products: • Moths • Carpet beetles Nuisance: • Lady beetles • Sugar ants • Box elder beetles
- 39. Samples of the insect and plant (if applicable) are essential for proper ID You’ll usually need adults • Larvae are very difficult Ken Gray Images: http://www.ipmnet.org/kgphoto/ http://entomology.oregonstate.edu/urbanent OSU Urban Entomology
- 40. Cockroaches: Often associated with apartments Health pests Fleas American cockroach German cockroach
- 41. Structural pests Carpenter ant Termites Require referral to PCO: “Pest” in yellow pages
- 42. Pests of stored products Indian meal moth Carpet beetles
- 43. Lady beetle Box Elder bug Nuisance insects
- 44. http://www.puyallup.wsu.edu/plantclinic/resources/pls-res.html http://entomology.oregonstate.edu/urbanent OSU Urban Entomology website: WSU Plant Disease and Insect Identification Pests Leaflet Series: Household insect websites
- 45. Spiders in the home
- 46. Only two venomous spiders in Oregon: • Black Widow • Hobo (Aggressive House Spider) Most clientele want to know if it is venomous Black Widow Aggressive House (Hobo)
- 47. Most spiders brought in are neither species Jumping Zebra Spider Spider ID not always easy • if it can be readily ID’d, do so • if it cannot be, do not!
- 48. General information on spiders, management: Oregon Department of Agriculture: http://oregon.gov/ODA/PLANT/IPPM/spiders.shtml The important facts are: • Spiders with few exceptions are non-toxic beneficials • Sanitation and structural modifications work best Washington State University: http://cru.cahe.wsu.edu/CEPublications/EB1548/EB1548.pdf
- 49. Vertebrate pests
- 50. Tree squirrel Mole Gopher Climbing and burrowing pests
- 51. Voles
- 52. Vertebrate pest information The Internet Center for Wildlife damage management http://icwdm.org/ Or…just use this link… http://digitalcommons.unl.edu/icwdmhandbook/
- 53. Cultural information OSU Extension Service Publications http://extension.oregonstate.edu/catalog/ Scholars Archive (older, non-reviewed publications) http://ir.library.oregonstate.edu/xmlui/
- 55. Two factors that affect ability to diagnose problems: 1. The perception of the caller of the problem
- 56. 2. Their ability to describe the problem accurately
- 57. An accurate diagnosis depends on good information… “Bring in a sample”
- 59. Photos give you an even better “picture”! Encourage clients to bring in pictures
- 60. What is the identity of the affected plant? Steps in diagnosing plant problems… Euonymus spp. Powdery mildew
- 61. Keep assessments of “damage” in proportion Zucchini (Cucurbita pepo)
- 63. • What are the characteristics of the plant? • How does it display them through the year? 1. Determine that a “real” problem exists Japanese Cedar (Cryptomeria japonica )with Incense Cedar (Calocedrus decurrens) in winter
- 64. Pinus contorta ‘Chief Joseph’ in winter
- 65. Western redcedar (Thuja occidentalis): foliar browning in fall
- 66. Pinus sp. in midsummer
- 68. Grape-pith color
- 69. Double file Viburnum (Viburnum tomentosum)
- 71. 2. What is the “population” of the plants? Arborvitae (Thuja occidentalis)
- 73. Boxwood (Buxus sempervirens), with Hebe (Hebe sp.)
- 75. Azalea cultivars (Rhododendron spp.): Powdery mildew (Erysiphe azaleae)
- 76. Kinnikinnick (Arctostaphjylos uva-ursi) 3. And…how many of the plants are affected?
- 78. 4. What is the pattern of damage within the population? Incense Cedar (Calocedrus decurrens)
- 79. Normal
- 80. Uniform pattern=abiotic factors (non-living) 1. Entire population uniformly affected Abnormal
- 81. Usually the result of non-living, environmental causes Uniform pattern Occurs over the entire population of plants, or discrete groups Periwinkle (Vinca minor)
- 82. Uniform pattern=abiotic factors (non-living) 2. Same part of entire population affected Abnormal
- 84. Foliar browning on Pinus, Rhododendron and Euonymus
- 85. Uniform pattern=abiotic factors (non-living) Abnormal
- 87. Random pattern=biotic factors (diseases/pests) Abnormal
- 88. Random pattern Occurs because of progressive spread of a living organism Oriental Arborvitae (Platycladus orientalis): Berckmann’s Blight
- 89. Turf: Cranefly (Tipula sp.) damage
- 90. Arborvitae (Thuja occidentalis): spider mites
- 91. Don’t overanalyze “uniform” versus “random” Arborvitae (Thuja occidentalis) near La Grande, OR
- 92. Petunia (Petunia x hybrida)
- 93. Japanese Cedar (Cryptomeria japonica)
- 98. 5. What part or parts of the plant are affected? Japanese Zelkova (Zelkova serrata)
- 99. Manzanita (Arctostaphylos ‘Arroyo Cascade’): Leaf gall aphid (Tamalia cowenii) Just leaves?
- 100. Red Maple (Acer rubrum): Anthracnose (Kabatiella sp.)
- 101. Apple (Malus sp): Scab (Venturia inaequalis) Leaves and fruit?
- 102. Blueberry (Vaccinium corymbosum): Mummyberry (Monilinia vaccinii-corymbosi) Leaves, fruit and shoots?
- 103. Cherry (Prunus avium), Coryneum blight (Wilsonomyces carpophilus))
- 104. Stem-tip dieback? Atlas Blue Cedar (Cedrus atlantica ): Needle Blight (Sirococcus conigenus)
- 105. Individual stems dying back entirely? Japanese Maple (Acer palmatum): Verticillium wilt (Verticullium dahliae)
- 106. The whole plant? English Walnut (Juglans regia)
- 107. Red Maple (Acer rubrum): Phytophthora Canker (Phytophthora sp.)
- 108. Birch: Betula utilis Hasn’t leafed out Normal Brown foliage
- 109. 6. What is the pattern of damage within the plant… Normal
- 110. Abnormal Uniform pattern=abiotic factors (non-living)
- 111. Abnormal Uniform pattern=abiotic factors (non-living)
- 112. Dwarf Alberta Spruce (Picea glauca ‘Conica’): sunburn
- 113. Rockrose (Halimium sp.): early-season tip chlorosis
- 114. Abnormal Random pattern=biotic factors (diseases/pests)
- 115. Noble Fir (Abies nobilis)
- 116. Rhododendron: Root Rot (Phytophthora sp.)?
- 117. Hawthorn (Crataegus laevigata): Leaf spot (Diplocarpon mespili)
- 118. 7. What is the pattern on the plant part? Normal
- 119. Abnormal Uniform pattern=abiotic factors (non-living)
- 120. Eucalyptus on Oregon Coast
- 123. Abnormal Random pattern=biotic factors (diseases/pests)
- 124. Rhododendron (Rhododendron sp.): Powdery mildew (Eriysiphe azaleae)
- 125. Beets (Beta vulgaris ): Leafminer (Pegomya sp.)
- 126. Maple (Acer sp.): Bladdergall mite (Vasates quadripedes)
- 127. Grape (Vitis sp.): Powdery mildew (Erysiphe necator)
- 128. Normal
- 129. Healthy Weeping baldcypress (Taxodium distichum ‘Cascade Falls’)
- 130. Abnormal Uniform pattern=abiotic factors (non-living)
- 131. Grand Fir (Abies grandis), Phenoxy herbicide damage
- 132. Arborvitae (Thuja occidentalis): Phenoxy herbicide damage
- 133. Abnormal Random pattern=biotic factors (diseases/pests)
- 134. Douglasfir (Pseudotsuga menziesii): Needle cast (Rhabdocline spp.)
- 135. Hemlock (Tsuga sp.): Hemlock woolly adelgid (Adelges tsugae)
- 136. 8. When did the symptoms appear? Peach (Prunus persica): Leaf Curl (Taphrina deformans)
- 138. Symptoms appear early in the year? Rosemary (Rosmarinus officinalis): cold injury
- 139. Viburnum tinus-sunburn Symptoms appear later in the year
- 140. Symptoms appear after specific event Wheat (Triticum aestivum): spray damage
- 141. 9. Are the symptoms spreading, improving or constant? 2007 2009
- 142. Port Orford Cedar (Chamaecyparis lawsoniana): Phytophthora root rot (Phytophthora spp.)
- 143. Aspen (Populus tremuloides) Leaf scorch
- 144. Symptoms stay the same Rosa Berries ‘N’ Cream™
- 146. Rhododendron (Rhododendron sp.): Sunburn Damage from non-living factors will induce symptom development, but there will be no signs of a pest 10. Are any signs of a pest present?
- 147. Symptoms: Physical characteristics of a problem expressed by the plant. Include: • wilting • leaf discoloration • leaf spots • leaf distortion • defoliation • galls • cankers • rots/dieback • “plant decline” Cucumber (Cucumis sativus): wilt
- 148. Holly (Ilex sp.): leaf discoloration
- 149. Western Spicebush (Calycanthus occidentalis): leaf spots
- 150. Redbud (Cercis canadensis): Leaf distortion due to phenoxy herbicide
- 151. European Pear (Pyrus communis): Fruit distortion due to true bug feeding damage
- 152. Fraser Photinia (Photinia x fraseri): defoliation by Leaf Spot (Diplocarpon mespili)
- 153. Birch (Betula sp.): gallForsythia (Forsythia sp.): Stem Gall (Psudomonas savastanoi)
- 154. Oak (Quercus sp.): mite galls
- 155. Alder (Alnus rubra): cankers (undetermined cause)
- 156. Peach (Prunus persica): dieback and canker
- 157. Tomato (Lycopersicon esculentum): rot caused by Late Blight (Lycopersicon esculentum)
- 158. Kousa dogwood (Cornus kousa) Plant decline
- 159. Goldenchain tree (Laburnum x watereri): aphids Signs: evidence of the actual causal agent Diseases: • fungal fruiting bodies • fungal mycelia • bacterial slime (more later…) Other… • rodent mounds/holes • slug trails Insects: • the insect itself • boring holes or tunnels • sawdust • frass…
- 160. Apple (Malus domestica): Crane fly (Tipula sp.) Is this really a problem?
- 161. Sunflower (Helianthus annuus): Sclerotinia wilt (Sclerotinia sclerotiorum)
- 162. Silk Tree (Albizia julibrissin) Nectria canker
- 163. Apple (Malus domestica): Rust (Gymnosporangium sp.)
- 164. Incense-cedar (Calocedrus decurrens): Broom rust (Gymnosporangium libocedri)
- 165. Big-leaf maple (Acer macrophyllum): Tar spots (Rhytisma punctatum)
- 166. Cherry (Prunus sp.): possible Bacterial canker damage (Pseudomonas syringae)
- 167. Apple (Malus domestica): Leaf roller (species undetermined)
- 168. Rhododendron (Rhododendron sp.): Azalea Lace Bug (Stephanitis pyrioides)
- 169. Hebe (Hebe sp.): Meadow spittle bugs (Philaenus spumarius)
- 170. Viburnum davidii: leaf notching due to root weevils
- 171. Colorado Blue Spruce (Picea pungens): White Pine weevil (Pissodes strobi)
- 172. Apple: (Malus domestica): frass of the Apple-and-thorn skeletonizer (Choreutis pariana)
- 173. Slug trails
- 174. Vole burrows
- 175. Some signs cannot be seen without magnification Red raspberry (Rubus idaeus): RBDV
- 176. Sweet Cherry (Prunus avium): possible Bacterial canker (Pseudomonas syringae)
- 177. Pear (Pyrus communis): Leaf spot-undetermined cause (stress? Fungal? Herbicide???)
- 178. Theory is great but, how do I actually do this???
- 179. What’s wrong with my tomatoes??? Photo #1
- 181. An intake form assists with problem solving: OSU Extension Master Gardener Client Information Form – Plant Problem Use this form to take down client information and to refer cases to the next MG shift. Name of Intake Person___________________________ Date____________AM____PM____ Client Name_____________________________________ Daytime Phone_______________ Mailing Address______________________________________________________________ (Street Address) (City) (Zip) Email Address______________________________________________________________ __ Provide information based on “Questions to Ask Clients” form in binder. (Use the back of this form if more space is needed) Type of Plant Tree__ Shrub__ Vine__ Herbaceous__ Evergreen__ Dedicuous__ Houseplant__ Name of plant, if known_______________________________________________________________________ Where is it growing? Indoors___ Outdoors___ Potted___ In ground___ Greenhouse___ In water___ Exposure Full sun__ Part sun/Part shade__ Full shade__ Soil Sandy__ Loam__ Clay__ Where is the problem on the plant?____________________________________________________________ How many of this type of plant do you have?_____ How many have this problem?______ Are any insects or mites present? Yes__ No__ If yes, how many?________________________ Fertilizer? Yes__ No__ If yes, what?_________________________________Applied when?_______________ Irrigation? Drip__ Soaker Hose__ Sprinkler__ Hand__ How often?_______________ Duration____________ Transplanted? Yes__ No__ If yes, when?____________________________ Sample Provided?__________ Describe damage/problem____________________________________________________________________ ___________________________________________________________________________________________ ___________________________________________________________________________________________ ___________________________________________________________________________________________ ___________________________________________________________________________________________ Any treatments or remedies applied? Yes__ No__ If yes, what?______________________________________ When?_______________________Result?_________________________________________________________ Answer & Client Notification MGs addressing this question: 1___2___3___ If question is not answered after 3 MGs have attempted to answer, pass question on to Home Horticulture Agent. Diagnosis or identification Recommendation Source(s) of information Client notified by ___________________Date________________Via phone_____Via mail____Via email_____ After notification: 1) Record completion in Daily Log. 2) Save Sample. 3) Place form in Archives loose-leaf. 2) The clues 3) Your diagnosis & how to solve 1) The client
- 182. Practice Questions 1. When should I fertilize my lawn and how much fertilizer should I apply?
- 183. 2. What kind of spider is this and is it poisonous??? Photo: http://en.wikipedia.org/wiki/Giant_house_spider#mediaviewer/File:Tegenaria_duellica_and_dollar_bill.JPG
- 184. 3. How do I plant a tree?
- 185. 4. How can I tell when my persimmons are ripe?
- 186. 1. When should I fertilize my lawn and how much fertilizer should I apply? Resources: • EC1278: http://ir.library.oregonstate.edu/xmlui/bits tream/handle/1957/18906/ec1278.pdf • EC1521: • https://ir.library.oregonstate.edu/xmlui/bit stream/handle/1957/51127/ec1521.pdf
- 187. 2. What kind of spider is this and is it poisonous??? • It’s probably not a hobo spider! • http://pep.wsu.edu/pdf/PLS116_1.pdf
- 188. 3. How do I plant a tree? • What kind of tree? (right plant, right place) • EC1438: • http://ir.library.oregonstate.edu/xmlui/bits tream/handle/1957/19522/ec1438.pdf
- 189. 4. How can I tell when my persimmons are ripe? • Question: What kind of persimmon is it? • http://aggie-horticulture.tamu.edu/fruit- nut/files/2010/10/persimmons.pdf
Editor's Notes
- The purpose of this presentation is to familiarize Master Gardener trainees with the process of assisting homeowners with home and garden problems. It reviews the types of enquiries Master Gardeners are expected to deal with and those to pass on to Agents and other community specialists. It will cover in broad detail the types of enquiries Extension offices receive. There is a more detailed section on the process of resolving plant problems, as well as a discussion of cultural problems which are common in gardens and landscapes
- This is an effort to categorize the types of enquiries Extension offices receive from homeowners in general terms. The discussion that follows roughly follows these categories.
- One of the principal difficulties in solving plant problems is getting enough accurate information from the client to allow for a correct diagnosis. People differ greatly in their ability to provide relevant information on the problem and description of the symptoms and signs. If the contact occurs over the phone rather than in the office it is even more important to use a systematic approach when talking to the client to extract relevant information from them. Not being able to visit the client can be a problem but this is not always an impediment to solving the problem
- This form is copied and available at the Desk. The purpose of the form is to assist the MG volunteer in gathering basic information on the characteristics of a plant problem, the growing environment and cultural practices that will assist in solving the problem. The questions on the form correspond roughly to the questions to ask in plant problem diagnosis later in the presentation.
- There are lots of ways to provide a client with an answer. The types of information we provide include a verbal description on the phone, photocopies or often they are OSU Extension Publications. It’s fine to direct the client to the Publications website if they have Internet access, rather than print and mail to them.
- Master Gardeners are expected to solve home garden problems only. If the client turns out to be a commercial grower, they should be referred to the appropriate agent for the commodity. This list is posted at the MG desk for reference and is updated annually.
- For the most part, any enquiry that has anything to do with health issues should not be handled by Master Gardeners, but should be referred to medical health professionals. We deal with gardening problems. The photo at top left shows a poison oak plant, which can cause dermatitis. Providing information on therapy for poison oak exposure, or other poisonous plants, would not be appropriate for MG’s, but information on managing the plants is okay. Also, when clients call and the enquiry is apparently about a troublesome neighbor, it’s best to refer these to the Agent or to municipal government with jurisdiction in that area.
- A comprehensive soil test which includes soil pH, organic matter content, major nutrients (P, K, Ca, Mg etc.) and salt content can be done by a lab for around $45. This is much more thorough and helpful to the client than a simple pH test, which are sometimes requested, and the results are likely to be a lot more accurate, too. A publication on laboratories that do soil and water tests (and other tests) is available from OSU Extension Publications, EM 8677, “Laboratories serving Oregon”. Another useful publication is EC 628, “Soil sampling for home gardens and small acreages”.
- It is important for volunteers to realize that they are not alone in the effort to answer these questions. In Linn & Benton County, volunteers have veteran Master Gardeners upon whom they can call for assistance, including those with specialized training in entomology and other fields. If a volunteer is not satisfied with their knowledge of a problem and ability to solve it, they are told to leave it for myself, the community horticulturist. I will take up the enquiry and if I can’t solve it, then I can call on a crop specialist for the commodity in question or utilize the Plant Clinic, Insect or weed identification services if necessary. It’s important to point out that this network of resources means that we can almost guarantee our clients a very authoritative diagnosis to their problem.
- It is important for volunteers to realize that they are not alone in the effort to answer these questions. In Linn & Benton County, volunteers have veteran Master Gardeners upon whom they can call for assistance, including those with specialized training in entomology and other fields. If a volunteer is not satisfied with their knowledge of a problem and ability to solve it, they are told to leave it for myself, the community horticulturist. I will take up the enquiry and if I can’t solve it, then I can call on a crop specialist for the commodity in question or utilize the Plant Clinic, Insect or weed identification services if necessary. It’s important to point out that this network of resources means that we can almost guarantee our clients a very authoritative diagnosis to their problem.
- Remind the students that each County office submits a report to Gail Langellotto each year, and she will compile the Statewide report for the Master Program. Part of the report includes the number of contacts for the Desk, which should be recorded and then summarized each year. This is a good database of information on the types of enquiries received, too.
- Requests for plant identification are pretty common. This is also the first step in solving a plant problem, so a knowledge of resources for identifying plants is important. The plant pictured is Myrtlewood, Umbellularia californica, which often appears spontaneously in gardens in western Oregon and is often brought to Extension offices for ID.
- Requests for plant identification are typically of three types. People move from other areas of the US to the Salem area and are not familiar with the landscape plants in their new residence, so want to know what they are. Or, much like the Myrtlewood in the previous slide, a plant appears suddenly in their yard and grows like crazy and they want to know what it is (prior to getting rid of it, usually). Or third, it is a weed problem they want to identify and eliminate. The photo shows a batch of plant samples brought by one client to Marion County for ID!! Usually it is onew or a very few plants… There is a plant ID service through the Department of Botany and Plant Pathology in Corvallis. Plant samples, or (photos of plant samples by email) can be sent to Dr. Richard Halse for identification at no charge.
- There is a very comprehensive website for landscape plants housed in the horticulture Department which includes a search engine to assist with ID.
- Clients will often bring in a single leaf from their plant asking for identification and this is only rarely possible. A stem section with multiple leaves is the minimum required and plant specimens with flowers can almost always be correctly identified. Plants in fruit are next best. The photos show Chokecherry (Prunus virginiana) and Strawberry Tree (Arbutus unedo) in the top right and bottom left, respectively. Both good samples. Other information on the plant is often helpful and a plant sample submission sheet is available at the OSU Plant Clinic website, http://www.science.oregonstate.edu/bpp/Plant_Clinic/index.htm.
- This shows examples of two trees which are commonly brought to the Extension offices in Marion and Polk Counties for ID. Both are planted as ornamentals and both occasionally seed themselves in peoples gardens. What both these plants have in common is that the seedlings appear and then grow very quickly and have very large leaves, which really causes people to wonder what they are.
- The photo shows a young plant (perhaps two years old) of Paulownia tomentosa, Empress of India Tree, which appeared in a clients yard. See why they get concerned?!
- For weed identification the same criteria of stem section and flower is important. Sometimes when the media report on new noxious weeds, clients will bring in lots of samples of what they suspect may be the weed in question, although it often is not.
- Many requests for mushroom identification are received in Extension offices, particularly in the fall, but they can come in any time of the year.
- Requests for mushroom identification really boil down to whether the mushroom in question is toxic or whether it is good to eat. Those clients concerned about toxicity often see mushrooms popping up in the lawn or in flower beds and are concerned that curious children or pets may try eating them. They often want to eradicate the mushroom from the yard. However, it is not possible to do this. The mushroom is merely the spore-bearing structure of the fungus which is residing in the soil. Eliminating the fungus from the soil, and therefore any future mushrooms, is not possible or desirable as fungi are components of a healthy soil. So, the best remedy is to simply rake up the mushrooms as they are seen. If the client is asking about edibility, it gets particularly tricky. Some mushrooms are pretty distinctive, such as chanterelles. However, most others are not, and this includes some genera that contain both edible, and not-so-edible, or even poisonous mushrooms. Also, people’s tolerance for mushrooms varies and what some people find edible, others find give them gastro-intestinal distress. This does not even take into consideration the considerable variation in species of mushrooms that can occur in a given area, so that what appears as one species may actually include more than one that may vary in edibility. It’s generally unwise to rely on volunteers to identify mushrooms for edibility. I have a specialist on campus identify them for me, however, in cases where the client wishes to know about edibility, we restrict our decision to the mushroom they submit-we cannot be sure of others that may still be in the yard from which the specimen came.
- If clients are interested in learning more about mushrooms, especially those interested in edibility, they need to get involved with reputable enthusiast organizations where they can benefit from the collective experience of members and become more knowledgeable.
- Another type of question that is commonly asked is about the presence of moss and lichen on plants. Much like some types of plant ID questions, the clients asking about these may have gardened in drier climates than the Willamette Valley, where moss and lichen are less abundant than they are here.
- Moss and lichens are not pathogenic on trees in the way that plant diseases are, since they are merely growing on the bark of the tree or shrub and use it as a support. They are not parasitizing the plant for water or nutrients in the way that parasitic plants do. Lichens and moss clearly grow more lushly on some trees and shrubs than others, but essentially any plant in our area will have some growth of these after a few years. It is not necessary to remove these to assist the tree, although it is possible to physically remove it if the client finds it undesirable. It is worth pointing out, though that it will grow back if the environment remains the same.
- Moss on roofs is generally considered undesirable because it is thought to harm the roof. A lot of information on moss control is available at the website!
- Moss is detrimental to lawns and should be controlled, although it is also a common component of lawns west of the Cascades.
- An example of a definite problem on a plum leaf, covered with aphids, cast aphid skins and honeydew. The link is to the PNW Insect Management Handbook website.
- Bronze Birch borer is common east of the Cascade Mountains but since 2003 has been found on the west side of the mountains. It will attack several birch species, but is especially attracted to two of the most commonly used species, Betula pendula and B. jacquemontii. The photo shows a stand of trees along Van Buren Street in Corvallis, where the closest two trees are significantly stressed.
- Also of great importance these days is an understanding of the spotted wing dropsophila…
- Many insect enquiries are received in Extension offices yearly, and most of those involve insects in the home. The various pests can be grouped into several broad categories.
- Insects cannot be identified over the phone, and therefore, for correct identification, a sample will have to be provided to the MG volunteers in the office. The sample should be as complete as possible. Adult insects are usually required. Sometimes larvae can be identified, though it is often more difficult.
- Structural pests are those that excavate wood within the home. Positive identification of these pests makes it very advisable for the homeowner to consult with a Pest Control Operator (PCO). Home therapy of these problems are unlikely to be effective and the potential consequences of an untreated infestation are too great to leave untreated.
- Insects such as the Indian Meal Moth are usually introduced to the home on infested products and then proliferate and spread to other products within the home. Control of these pests, and similar types involves finding infested products and eliminating them systematically from the home, which can be a time-consuming process. Regular cleaning and re-inspection is typically required until the pest is gone.
- Nuisance pests are those that are not structural or human health pests and do not feed on fabrics or stored products. They simply find their way into homes in annoying numbers. The most common are ladybeetles and box elder bugs. Box elder bugs and ladybeetles often congregate on the side of homes in fall and cause people to call the office for control options.
- As was discussed in the last lecture, the first thing to know is the identity of the host plant. I have seen problem diagnosis books that suggest this is not necessary, but this is basic information that will help you diagnose the problem, not to mention ensure that the plant is growing in the conditions that are suitable for it.
- The first thing to keep in mind once the plant is identified, is that plants are living things so they will from time to time show stress. However, this does not mean that the plant is suffering from a disease or insect pest, often it is part of the normal process of growth. The squash plant in the photo does have a discolored leaf, but in general the foliage looks very healthy and the upper part of the plant, near the growing points, looks fine. Unless the condition of the plant deteriorates, there’s really no reason to be concerned about it’s health. This principle applies in any situation be it home garden, landscape or agricultural.
- On the other hand, this is also squash and we would call this a problem, and in this case the majority of the leaves are affected by powdery mildew, a fungal disease.
- This is one of the reasons why it is important to know the identity of the host plant. It will enable you to find out the characteristics of the plant. The example here shows a pair of cedar-like conifers photographed in January. The tree on the left is Japanese cedar (Cryptomeria japonica) and the tree on the right is Incense cedar (Calocedrus decurrens). The Japanese cedar has turned a distinct reddish brown color and in comparison to the Incense cedar may look stressed. In fact, some selections of this tree simply turn this color in winter in response to cool temperatures, and with warmer weather in spring, the tree returns to a bluish-green color.
- Color changes like this are not really that uncommon on some conifer species and in some cases, like the Japanese cedar, are considered to be desirable ornamental characteristics. This photo shows a selection of the lodgepole pine called ‘Chief Joseph’. The photo was taken in winter when the entire shrub turns a bright yellow color. In spring, it reverts to being the more typical green color for this species. Winter color like this is very dramatic, but more subtle changes occur on some common landscape plants like Arborvitae, Yew, cedar and junipers and are perfectly normal.
- Here’s another example which shows foliar browning on a western redcedar. The photo was taken in October at the end of summer and the brown foliage is found distributed throughout the canopy. The important thing here is that it is the interior foliage exclusively which is showing the stress and not the newer growth. These are older leaves which are ordinarily shed near the end of the rowing season in response to the normal summer drought of the region as well as shading of the interior leaves which occurs as the canopy grows. So although the foliage looks “dead”, this is a normal response of the plant to it environment. The follow-up picture shows the same plant in June of the following year-note that at this time of the year, following the winter and spring rains, no dead foliage is visible.
- This however, is not normal. This photo was taken of a pine in midsummer and as you can see, most of the foliage is brown. Definitely not a normal state of affairs for a pine, or for that matter, any other conifer, in the middle of the growing season.
- This photo depicts a crape myrtle in May in the early stages of growth. If you look at the shoot tips, there is no growth evident and they appear dead. On this particular plant, this condition is normal, because crape myrtle flowers at the tips of the current season’s growth. So this dead are is where the flowers, and any seed pods, were located last year. As with any flower and seed producing structure, this growth dies following one growth cycle. The following spring, the plant resumes growth from vegetative buds below the former flowering structure, which you can see on each shoot several inches down from the tip.
- Here’s another example that could be perceived as a problem. The photo shows a pair \of grape stem sections. The tissue in the center of each stem section (click) is known as the pith. These tissues serve to store and transport nutrients within the plant. In new shoots, the pith is often white, but as the shoot agers it may have a tendency to turn brown. This is a natural process and should not be regarded as a problem.
- In many ornamental flowering shrubs such as this Viburnum, you may observe discoloration of the foliage on parts of the plant as the summer progresses. In this example, some of the uppermost leaves have turned a reddish color (click). Beneath these reddish shoots are a cluster of green shoots which ar not discolored (click). The change in color is a stress reaction by the plant, but it is not unusual. If one were to look at the shoots that were affected, you would find that they were the shoots on which the flowers were borne in the spring, and on which seeds and fruit are now developing. The green shoots lower down are vegetative this year and will bear flowers and fruit next year. Compared to the green shoots lower down, these upper shoots are under more stress because of the fruit and are discolored as a result. Variations in foliage quality like this are not unusual on other flowering shrubs that produce new shoots like this including Mock Orange, Forsythia and Weigela.
- In this photo is a section of tomato stem and I have had clients express concern that these “bumps” (click) are a sign of a problem, and that like warts, they require removal. In fact, they are simply the beginning stages of root development on the stem. In most cases they are quite harmless, and in fact it is this characteristic that allows one to plant a tomato in the ground much deeper than it was grown in its pot.
- The next question to ask is that you have an affected plant or plants, and this is part of a population of the same species or possibly even the same cultivar. So you want to define how numerous that population may be. It will vary widely depending on the situation. In the photo is an arborvitae hedge. Some of these are showing stress or are actually dead. So the “population” is all the arborvitae, affected or not, which consists of about 23 individual plants in the photo. Although there are other plants visible, including a pine and a flowering plum, these form separate “populations” from the arborvitae. The importance of this is that cultural requirements of plants vary widely and when different species are put together in one environment under a particular type of management they may respond differently. Also, diseases and pests tend to be specific to individual species or even cultivars of plants and so it is very helpful to identify the total affected population of plants. It would be unusual, but not unheard of, for multiple populations of plants in one area to be showing the same symptoms. In the photo though, the problem seems to be restricted to the arborvitae.
- Depending on the situation, there may be as few as one plant in the population, or there may be thousands. And as the previous example showed, there may be more than one population of plants present. Following are some examples. Maybe the simplest population example is the wheat field in the photo. Like many field crops, wheat is grown in large blocks, typically of one cultivar. This field extends a considerable way into the distance to approximately the white line and appears entirely uniform. Given how wheat is seeded and grown, it almost certainly consists of one cultivar of wheat, so here we have one population which in this case consists of thousands of individual plants.
- In other situations, there may be groups of different species which form distinct populations. this landscape example, there are 4 distinct populations present, each of which is planted in parallel rows. In the foreground (click) is Periwinkle, the latin name of which is Vinca minor. Behind that (click) is an azalea, then (click) Viburnum davidii then (click) Cherry Laurel, the latin name of which is Prunus laurocerasus.
- Here is an example of the difference in response of two different populations of plants to injury. The two populations are planted alternately in a row in this garden near Salem, OR. The green plants (click) are boxwood, and the (click) brown plants between them are Hebe. Both of these are broadleaved evergreen plants, however the Hebe plants have dropped all their leaves and appear to be dead. This photo was taken in the spring after a particularly cold winter and the damage to the Hebe plants was because of cold temperatures. By comparison, the boxwood plants show no injury whatsoever. A bit of research on these two different plants would show that even though both are broad-leaved evergreen landscape plants, the boxwood are usually considered hardy to temperatures below 0F. Hebes, by comparison, may be injured by temperatures of only 20F, depending on cultivar.
- In other situations, you may be dealing with a single species but there may be multiple cultivars of that species present. Here is a commercial planting of highbush blueberry which was photographed in the fall, as the leaves are turning color. There are many cultivars of highbush blueberry, and in the photo, three separate populations can be seen, which can be differentiated by the variation in fall color (click x3) . These cultivars will also vary in many other characteristics, including size of the plant, fruit ripening time and as was mentioned previously, cultural requirements and susceptibility to diseases and pests, so they must be treated as separate populations.
- Here’s another landscape example which is quite common. In this photo the shrubs present all appear to be Rhododendron (click) but it appears that there may be more than one cultivar of each. It looks like there are three distinct groups, which appear similar enough to be regarded as the same cultivar. Looking at the plant in the foreground, the first group (click) is the red-flowered shrubs, the next group (click) is the low-growing pink flowered shrubs, and the third group (click) is the pair of shrubs which are yet to come into bloom. If you look farther back in the photo, there may be more of each of these, but in the foreground what we have are three different populations of Rhododendron. If you are examining this landscape for problems, then each of these populations may show different susceptibility to various environmental, cultural, disease or insect pest problems.
- The variation in response by different species within a genus and also different cultivars of a species can be illustrated by this example. In the photo are a pair of azaleas growing side by side. The plant on the right is a silvery color because of a severe case of Powdery Mildew. The plant on the left on the other hand is entirely unaffected by the disease.
- To get an idea of the extent of the problem within a population, you want to know how many of the population are affected. How you estimate this will depend on the population in question. Here we have a population of Kinnikinnick being used as a groundcover. At least, they are attempting to use it as a groundcover, but as you can tell from the picture, a number of the plants are not healthy. As was noted earlier, there are different cultivars of kinnikinnick on the market, but given that most landscapes involve planting solid blocks of one cultivar, we will assume that all of these are one cultivar and so they constitute a single population. Of the approximately 35 plants visible in the photo, at least half of them are showing lack of vigor, yellowing or browning of tissues. Some are completely brown and are likely dead. When you are attempting to establish which plants are affected in this population and which are not, you should include any plants which are showing symptoms of the abnormal condition. So in this photo, there are some individual plants that are completely brown (click), and others which are showing chlorosis and a bit of foliar browning. (click). Since there are plants in various stages between these two, it would appear that they are all suffering from the same problem. So in estimating the number of affected plants, you should include all those exhibiting symptoms between these extremes.
- In the photo is a field of grass, and part of this large field is affected by some sort of dieback. Rather than try to estimate the number of affected individual plants in a situation like this, you would provide an estimate of the percentage of the total field that was affected.
- Once the population of plants is defined and the affected plants within that population identified, it is very helpful to look at the location of the affected plants within the overall population and the pattern that they create. The pattern of damage can often help in defining the possible cause of the problem. Damage can be either appear in a uniform pattern within the population of plants, or it can appear in a random pattern.
- The illustration above is a representation of a population of plants, essentially the same species of tree. In the “normal” population, all of the trees look green and healthy without obvious signs of serious problems.
- In this example, all of the trees have turned a yellowish color, and so can all be said to be more or less equally affected by whatever is causing the yellowing. This is an one example of a uniform pattern of damage, where all the plants in the population are similarly affected. Uniform patterns of damage are often associated with what are known as abiotic problems. These are problems resulting from environmental or cultural factors, which can cause large-scale changes in growing conditions. Environmental factors include things like sudden changes in weather, which of course may affect an area much bigger than the plant population itself occupies. Therefore the entire population will show the same symptoms. In some cases, the change may occur simultaneously on the entire population.
- Here is an example of a uniform pattern of damage in this landscape. The groundcover being used here is periwinkle (Vinca minor). This is a low-growing, spreading plant so the population consists of possibly a couple of hundred plants. When grown in part shade on periwinkle is a medium green color (click). However, when it is planted in full sun, it often shows considerable chlorosis In this example, the entire planting is growing in full sun and has turned more or less uniformly yellow. There may in addition be soil quality issues such as lack of nitrogen contributing to this but overall this is a uniform pattern on the whole population as the result of an environmental problem.
- A uniform pattern of damage does not mean that your entire plant will show symptoms of a problem. It may mean that the same part of all the plants in the population will show symptoms. In the example, one side of all the trees show some browning, whereas the rest of the tree looks normal.
- Here’s what such a pattern might look like in a population. The photo shows a hedge of arborvitae, most of which are showing browning of the lowest foliage on the plant. Not coincidentally, there is a strip directly beneath all the affected plants from which the grass has died back. It would be unusual to see such a pattern from a disease or insect pest. Instead, the reason for this pattern is that glyphosate herbicide was used to kill the grass and weeds at the base of the hedge, but the herbicide was applied carelessly, impacting the hedge as well as the grass. If you look at the Arborvitae plant in the immediate foreground there is no spray damage, but the grass is also right up at the base of the shrub. These types of damage are not at all uncommon where herbicides have been used a bit recklessly.
- Even more convincing evidence that you are looking at some sort of environmental or cultural problem is where you see the same pattern of damage on the same part of the plant on multiple populations. In the photo above is a landscape planted alternately with a topiary pine (click) as well as a Rhododendron (click) and a dwarf Euonymus (click)-three separate species therefore three separate populations. For some reason, probably related to the work on the siding of the building, the tops of all these plants showed browning of the foliage to a greater or lesser degree (click). I am unsure of the actual cause, but if I were asked what was the matter with these plants I would certainly suggest that it was related to the work being performed on the building.
- Another situation which can occur is where a distinct part of the plant population will show symptoms of a problem. Often the affected part of the population is associated with different environmental conditions or perhaps cultural methods than the rest of the population. In the example, one side of the planting is showing yellowing, whereas the remaining plants do not. It is possible that the soil quality is different where the affected trees are growing, or the irrigation system is not reaching those plants, or they are growing in a poorly drained area, or some other similar type of environmental problem. If this pattern was to appear in an actual planting, the symptoms that the plants were displaying would provide clues as to the source of the problem.
- Here’s an example of a problem affecting a discrete part of a plant population. The photo above is of a lawn in western Oregon and was provided by a client who was concerned about “brown patches in the lawn” in summer. The lawn in question stretches out on both sides of the driveway and is only partially visible in the photo. When one hears the term “brown patches in the lawn” it implies brown areas distributed throughout the lawn (click), as in this photo, in which a homeowner used glyphosate to spray out dandelions in the lawn, killing the dandelion, but also any grass the herbicide contacted as well. (Click). But this was not the case. When the photos of the lawn were forwarded, they showed that all of the brown areas were clustered around the driveway, not in other areas of the lawn. This is also a classic uniform pattern, where the affected plants are growing under cultural or environmental conditions different from the unaffected plants. In this case, there are several reasons why the grass might be brown next to the driveway. For one thing, when asphalt is installed, it is typically over a bed of crushed rock which likely extends in places past the asphalt itself. So it’s possible that some of the grass is growing in a very porous gravelly soil that does not hold water well, contributing to drought stress. It’s also possible because of the way irrigation systems are installed, that the grass nearest the driveway is receiving less water than the grass elsewhere. And contributing to the problem is the fact that the asphalt will get very warm in summer, adding to the heat stress on the grass growing adjacent to it. Any of these issues could cause the problem on this lawn.
- The other type of damage pattern that occurs in plant populations is a random pattern. This type of pattern is characteristic of biotic plant problems, those caused by living organisms such as disease and pest problems. This pattern arises because of the way these organisms affect a plant population. They tend to begin in a part of the population, then over time spread to the parts of the population, often in no discernable way, so affected plants appear scattered through the population. Over time the population will include plants that show serious symptoms from prior infections mixed with those more recently affected showing milder symptoms and some which show no symptoms at all.
- In the photo is a hedge of Oriental Arborvitae (Platycladus orientalis). Within each plant is a patchwork of brown patches caused by Berckmann’s blight, a fungal disease that causes death of the foliage on the shoot tips. If you look at the distribution of the brown patches in the three plants visible in the photo, you can see that the three are not equally affected by the problem. Since this disease kills foliage, observation of the hedge over time would show that the brown patches changed over time and in fact what typically happens with this disease, if it is not controlled, is that more and more of the foliage is affected and the disease causes dieback of parts of the canopy.
- Here’s another example, this time with a lawn affected by cranefly. The larvae of this insect feed during the winter months on the roots of turf. In most cases, they are present in small numbers so this activity may cause some thinning of the turf. In some cases, the larvae are sufficiently numerous to cause dieback of parts of the lawn, or in rare severe cases, death of much of the lawn. The photo above shows a fairly severe problem with obvious dieback of parts of the lawn, but notice the random distribution of the damage, which you would expect for a pest like this.
- Here’s another problem with a biotic cause. In the photo is a hedge of arborvitae and in the photo you see a patchwork of green and brown areas. The browning of the foliage is caused by spider mites, which feed on the foliage, causing it to discolor. Looking at the canopy of the hedge, you can see the haphazard distribution of the browning. Some plants are affected totally, some not at all and others have portions of their canopy affected.
- Weeds are not strictly speaking a plant problem, but they can cause problems for cultivated plants. Weed problems are of course biotic, so they tend to appear within a population randomly and spread over time.can be a plant problem, too, and these tend to pop up in fields or landscapes and if not controlled, have the capacity to spread just as diseases and insect pests do.
- Often a random or uniform pattern of damage in a plant population can be helpful in narrowing the source of a problem,, but keep in mind that these represent one aspect of the problem and other information will be required to determine the cause. Not every example of uniform damage can be attributed to environmental or cultural problems, and sometimes what appear to be random patterns are caused by environmental causes. One example of this is in the photo above, which is an arborvitae hedge photographed in eastern Oregon. The lower foliage on all the plants is missing and the cause is feeding damage by deer. In this area, winters are cold and there is little foliage available in the winter so most individual plants or hedges show this type of damage. The pattern on the plants is obviously uniform, but feeding damage by deer is definitely a biotic problem.
- Another example of this is the Petunia in the photo. The foliage from the center of the plant out to near the tips of each of the visible shoots on the plant had disappeared. This was also a very uniform pattern of damage but again in this case the problem was of a biotic nature. Slugs were responsible for the damage and had eaten the foliage at the base of each shoot.
- This photo shows a hedge of Japanese Cedar in November, following the long dry northwest summer. The population of these plants shows a haphazard pattern of browning. Notice that this is quite different in appearance from the uniform reddish color that these shrubs produce in winter, so it appears to be due to a different cause. The random pattern of the damage might lead to the conclusion that a disease or insect pest was responsible. However, this is where knowledge of the plant and it’s cultural requirements are very helpful. This is not a Northwest native plant and in fact is native to China and Japan, both of which feature climates with significant summer rainfall. Transplanted to the Northwest, these plants do best in irrigated landscapes. This population was not irrigated, and the appearance of the damage at the end of summer was strong evidence that drought stress was the cause. The random pattern of damage could be attributed to differences in soil quality and soil moisture availability between individual plants and it is possible that symptoms would continue to worsen on lightly-affected plants, so that ultimately much of the hedge would in fact show symptoms.
- Photo taken in Salem, OR in August. This is actually a uniform pattern caused by mis-function of an irrigation system. The risers are at the top of the lawn (on the left) and some of them worked better than others. The big brown patch was simply not getting any water. Note the line running across the lawn making the boundary between working irrigation, and non-working. Biotic pest problems rarely result in such distinct patterns
- Photo of Rhododendrons, several cultivars, taken in Corvallis, OR in February. Non-uniform pattern evident here with a range of symptoms of what appears to be root rot.
- Photo of a maple near Dallas, OR of a red maple tree with a longitudinal split in the bark on the main trunk. The damage was found not only on this tree however, (click) the driveway was lined with these same species of tree and each tree had a similar split in the same general location. The southwest side of the trees showed the injury in each case, so it is cold injury, resulting in a uniform pattern of damage.
- Mixed planting of a conifer and the broadleaved evergreen shrub in Monmouth, OR, pictured in February. The little bright green shrubs are fine, however, the conifers are in varying stages of distress, probably due to some sort of root rot. This site was very wet. The pattern is non-uniform on the conifers.
- I call this “redneck blight”. Parallel tracks in the field caused by someone driving out there…and evidently sinking into the muck. Picture taken at Ankeny Hill Wildlife Reservation in late winter. Uniform….
- Whether you are dealing with a large or small population of plants, you will want to establish what parts of the plant are experiencing the problem in question. Where on the plant the symptoms are located is an excellent indicator of what the problem might be
- Some problems are restricted to the foliage of the plant and do not progress to cause damage to stems or fruit or other parts. An example of such a problem is the odd reddish swellings on the foliage of the manzanita in the photo. The galls are caused by the reaction of the plant to the feeding of the manzanita leaf gall aphid, which causes thickening and curling of the leaf as well as discoloration. This damage can be seen fairly commonly on manzanita and kinikinnick in Pacific coast states.
- Another example of a foliar problem is anthracnose, a fungal disease. Among the many mapl;e tree species, it seems like red maple is particularly susceptible, although this may be partle because thewy are so commonly used in landscapes throughout North America. The disease causes irregular necrotic spots on the foliage and as with leaf spot problems on many plants, affected leaves tend to fall from the tree after infection. This disease can cause cankers to form on the twigs, although the foliage is what is most visibly affected. Since this is a shade tree, the aesthetic damage to the leaves and leaf drop are undesirable, although the tree itself continues to grow quite well.
- In some cases you may observe damage to foliage and fruit on a plant. One example is scab, a fungal disease which is considered one of the most important diseases of apple. The disease gets it’s name from the circular, rough cracked lesions that infections produce on the fruit, which drastically reduce the quality of the fruit. However, leaves are also infected and these leaves ultimately have brownish-colored lesions and fall prematurely from the tree.
- Some problems may occur on multiple plant parts. One example of this is the fungal disease mummyberry, which affects blueberry. This disease affects the foliage, flowers, fruit and new shoots of the plant. Infected flowers turn brown and wither, much as if they had been frosted. Leaf and shoot growth expanding from newly opened leaf buds is blackened in the center and eventually wilts and dies. During early berry development, diseased fruits look like healthy ones, however as they approach maturity, infected fruit become discolored and fall prematurely
- On cherry and other stone fruit such as peach, the fungal disease Coryneum blight can cause flower, fruit, foliage as well as twig damage. In the photo above, you can see brown lesions on the fruit, on blighted flowers and also on the leaves. The small brown leaf spots the disease produces are scattered over the leaf surface and have a tendency to fall out, giving the disease it’s other name, “shothole”. Cankers are produced on the younger wood
- In some instances there may be obvious dieback of foliage and stem tissues extending from the tips of the shoot back into the plant. This is the situation on the Atlas Blue Cedar in the photo, is affected by the fungal disease needle blight. This disease infects primarily the current season’s growth, causing the needles and shoot to turn brown and die.
- Over time on susceptible plants, repeated dieback of new growth can weaken a plant and result in major losses in the canopy. The flowering cherry in the photo is considered to be susceptible to a number of fungal and bacterial diseases which if not treated can result is the patchwork of living and dead tissue visible on this tree.
- If one entire branch, or branches on a plant are showing signs of a problem, while the other branches of the plant are showing no symptoms, then it is important to look at the base of the affected branch for evidence of some sort of damage. The young Japanese Maple in the photo is pictured in the spring. These are deciduous trees, so all of the leaves visible are from the current season. As the photo shows, three of the branches leafed out and then wilted and turned brown. The remaining branches on the tee look fine. The first thing to do it this situation would be to look for evidence of physical damage of some kind at the base of the affected branches. Any type of damage which would restrict water movement into the affected branch would cause the wilting visible in the photo. However, once again it is important to consider the plant and it’s characteristics. Japanese Maple is perhaps one of the most sensitive landscape plants to the soil-dwelling fungal disease Verticillium wilt. This disease infects water-conducting tissues, restricting water movement and causing a characteristic pattern where leaves on one branch or one side of the tree wilts, while other parts of the plant remain unaffected. On this particular host plant, assuming no damage to the base of the affected branches is found, then the pattern of damage and known susceptibility to the disease point towards a Verticillium diagnosis, but to confirm such a diagnosis, further evidence would be required.
- On the left and right sides of the photo are a pair of English Walnut trees from a very old orchard which has since been subdivided into housing, leaving some of the trees in various landscape situations. These are deciduous trees pictured in early summer. On the left is a vigorous healthy tree while on the right is a very thin canopy and poor growth. Typically where the whole plant is affected, then the problem is likely associated with the root system, crown or the main stem (or stems) of the plant in question. The actual cause of the problem of the tree on the right was not determined. However, this tree is growing in an irrigated lawn, while the healthy tree is growing in an unirrigated flower bed. And it is possible that the added water and soil compaction from lawn traffic has contributed to root system problems or disease. Again, in order to make a positive diagnosis, evidence of damage to the root system or of a specific pest or pathogen would be required.
- The photo illustrates another whole-plant problem on Red Maple. The two trees above are the same cultivar and the photo was taken in August. One of the trees is showing premature fall color, which is often a stress reaction. The whole tree is showing this color, which leads us to suspect that the problem is root or trunk related. Closer observation of the trunk of this tree (click), shows cracking of the bark as well as weeping of a black fluid from these cracks. Also, there is a obvious narrowing of the diameter of the trunk, known as a canker (click) where this damage is apparent. The diagnosis of the problem was Phytophthora Canker, a fungus-like disease which can affect various shade trees.
- Here’s another example on a population of three white-bark birch, a popular deciduous landscape tree. If you look at the photo, which was taken during the growing season, it is apparent that one of the trees has failed to leaf out (click X2), one of them has leafed out and the foliage has since turned brown (click X2), and the third plant appears quite healthy (click X2). If we look closely at the trunk of one of the affected trees (click), then it also shows the cracking and black fluid found in the Maple example.
- Patterns of damage can be found within populations of plants, but in some situations, particularly landscapes, there may be only a single plant which forms the entire population. You can still use the concept of uniform or random patterns of damage on an individual plant to help narrow the potential cause of the problem.
- The next two examples illustrate how uniform patterns of damage might appear on an individual plant. In this case, one side of the plant is showing browning of the foliage.
- In this case, the uppermost parts of the plant is showing browning of the foliage while the remainder looks normal.
- The photo shows a popular landscape plant, the dwarf Alberta Spruce. The photo was taken at the end of the summer, and the brown needles on the plant are clustered on one side of the plant, which in this case is the south-facing side of the plant. The north side of the plant has very little or no brown needles. This is a great example of a uniform pattern of damage on the plant. In considering the cause of this damage, we could first of all consider the growing requirements of this plant. Dwarf Alberta Spruce grows well in many regions of North America, and generally requires only full sun, reasonably decent soil and some summer irrigation in summer-dry climates to grow well. This plant was growing in western Oregon, a summer-dry climate and was not irrigated at all. It’s not surprising that the plant would show signs of sunburn and drought stress under these conditions, and the damage would show up principally on the side of the plant exposed to the most heat, which is the south and west sides.
- Another example of a uniform pattern on a plant is the chlorosis evident on the tips of the shoots of this rockrose. If you look at an individual shoot on this plant (click), only the most recent growth at the shoot tip is chlorotic (click). The chlorosis appeared in spring as the plant was beginning to grow and then gradually disappeared as the weather warmed up. It was present strictly at the tips of the shoots and appears to have been a temporary deficiency of a nutrient, possibly sulphur or iron. As the weather and soil warmed, the chlorosis disappeared.
- A random pattern of damage is as you might expect characteristic of biotic problems like pests or pathogens. As in a population, the problem will surface in no particular part of the plant and then spread randomly to other parts of the plant over time, leaving a patchwork pattern of damage.
- The Noble Fir in the photo shows the pattern of damage we might expect from a pathogen or pest in which the damage is distibuted haphazardly in the canopy of the plant. If you look carefully at the photo, you can see a number of areas where the needles have turned brown and represent older infections. There is also evidence of movement of the problem to new areas of the plant, specifically on the bottom left (click), where the needles have turned chlorotic, but are not yet brown. This patchwork of older and newer infections are to be expected with biotic plant problems.
- The photo shows a landscape which features a large Rhododendron. On the plant, you can see the foliage in various stages of dieback or decline. The foliage on the bottom left has died back completely. Elsewhere it is a patchwork of discoloration which includes some actually healthy-looking foliage. It appears to be declining towards the dieback evident in the bottom left. It’s typical to see patterns of damage like this from root-rotting organisms on a wide array of evergreen shrubs, whether they be broadleaved or coniferous.
- As in the case of patterns within populations, it is always important to consider the host, the growing conditions and other factors in addition to the pattern on the plant when considering potential causes of the problem. In this photo are a pair of English Hawthorn trees photographed in September. As you can see in the photo, the trees have dropped virtually all of their leaves, well before you might expect that to occur. There is however a veneer of leaves at the shoot tips, which gives the appearance of a uniform pattern with a possible environmental or cultural cause, perhaps lack of water. However the leaves on this tree were falling off long before drought stress could account for the problem. In fact, this is a disease problem, specifically a fungal leaf spot. Leaf spot is especially prevalent in cool, wet spring weather, and serious infections cause major defoliation of the tree. The weather in the spring prior to this photo was very cool and wet. So even though the pattern on this tree has a uniform appearance, consideration of all the available information led to the conclusion that the problem has a biotic cause.
- Just as with patterns in populations of plants and with individuals, patterns show up on individual plant parts as well. If you are looking at an individual plant, you don’t necessarily expect all the leaves on that plant to be showing symptoms, depending on how extensive the problem is. Instead, look at the affected part of the plant, and consider what type of pattern of damage you see on leaves, stems, fruits or other parts.
- Using leaves for examples, in this case we have a situation where the edges of the leaf have turned brown the whole way around the leaf. This would be an example of a uniform pattern of damage on the leaf.
- How such a pattern might appear on a plant is illustrated by this Eucalyptus tree, which is growing close to the seashore in Oregon. If you look at the plant as a whole, it’s apparent that there is some browning evident on the foliage, and for that matter, some twig dieback, too. Looking specifically at the foliage, however, (click), you can see that part or all of the edges of most of the leaves are showing some browning and dieback. This is not unlike the pattern one might expect to see as a result of drought stress, but it is rare to see such stress on established Eucalyptus trees. Instead, this is damage due to salt spray from the ocean, which is only about 600 feet from the plant. On stormy days this plant would be subject to a lot of salt spray, which causes the characteristic marginal necrosis on the foliage.
- Here’s a very characteristic type of pattern from drought stress on a Hosta, which typically will not tolerate any prolonged period of dry soil. The leaves all show a marginal necrosis and it is not unusual for the edges of the leaves on many plants to show this pattern of damage in response to inadequate water.
- Uniform patterns of damage may also show up on fruits. One end of each of these tomato fruit has a necrotic spot, while the remainder of the fruit looks normal. The end of the fruit opposite the stem is called the blossom end and this disorder is called blossom end rot. The disorder is caused by a lack of calcium in the fruit, which results in the characteristic damage. Tomatoes growing in soils low in calcium or in soils where moisture supply is uneven may show this disorder.
- A random distribution of symptoms on plant parts is once again more characteristic of biotic plant problems. Although a leaf is shown in the illustration, random patterns may appear on flowers, fruits or other plant parts such as twigs or stems.
- The light-colored blotchy lesions irregularly distributed on the foliage of this Rhododendron are caused by the fungal disease powdery mildew. Unlike the symptoms of damage produced by abiotic problems, there is no consistency in symptom development from one leaf to another with a biotic problem like this.
- The same sort of irregular pattern can be expected with insect pest problems on the foliage of plants. In this example the beet leaves in the photo have winding tunnels excavated between the upper and lower leaf surface. The affected tissues turn white and ultimately brown with time. The cause is the larva of a small, fly, the beet leafminer, which lays eggs on the foliage of beets. The larvae hatches and burrows between the lower and upper leaf surfaces feeding on the interior leaf tissue and giving the pest it’s common name of leafminer.
- Another familiar sight is the strange galls created on the foliage of maple and other plants caused by the feeding activity of certain species of mites. In this case, the feeding activity of a very tiny mite, the bladder gall mite on the underside of the leaves causes the development of the very bright red galls on the upper leaf surface. As you might expect, the mites feed in no particular part of the leaf so the galls are distributed randomly over the leaf surface.
- The same sort of random pattern can happen with biotic problems on fruit. The cluster of grapes in the photo is affected by powdery mildew, which is a common fungal disease problem of grapes. The disease causes cracking, wilting and rot of the fruit and in the cluster pictured, you can see fruit in various stages of infection on the same cluster.
- Conifers will display patterns of damage in the same way that broad-leaved plants will.
- Healthy foliage on conifers will not display distortion or discoloration. It’s always possible to find a few damaged needles on any plant, but the foliage will for the most part look free of defects and there certainly won’t be any noticeable pattern of damage.
- The illustration shows discoloration on the tips of all the needles, which would be considered a uniform pattern of damage.
- Notice the pattern of damage on the individual needles of this Grand Fir. They are somewhat chlorotic with a very distinct brown tip. Notice also, that it is the current-seasons growth (click) , found at the shoot tips, that is affected in each case (click). The previous seasons growth and any earlier growth that is present, does not show any evidence of damage (click). This is typical of damage patterns on evergreen coniferous plants caused by phenoxy herbicides. The herbicides do not affect grasses, and are commonly used in home and agricultural situations for control of broadleaved plants in lawns or brush.
- Phenoxy herbicides can cause the same sort of damage on conifers with scale-like needles such as arborvitae, but it’s not quite as obvious since the distinction between one years growth and a subsequent years growth are more subtle. Nevertheless, the most recent growth on these plants is at the shoot tips, and on the left in this photo you can see the browning and chlorosis found on the fir in the previous example. Healthy foliage from an unaffetected plant is on the right.
- As with broad-leaved plants, with conifers the same random pattern of damage can be observed on foliage and other plant parts. The illustration above shows a patchj work of damage on some needles, with others remaining unaffected.
- Notice the irregular pattern of damage on the needles of this douglasfir sample which is affected by Rhabdocline needle cast. This fungal disease starts as minute yellow spots on upper and lower surfaces of current-year needles. The spots become larger and darker during winter. By spring, spots may coalesce and become deep red-brown with a mottled appearance. Infected needles fall off by late June. This disease is a cosmetic problem because of the needle discoloration and the needle loss that occurs.
- Random patterns of distress can also occur on the foliage and twigs of conifers affected by insect pests. In this example, a hemlock is affected by the Hemlock woolly adelgid, and aphid-like insect that feeds on the needles, causing them to drop prematurely. The white patches in the photo are colonies of the adelgid, which produces a white, waxy material to protect itself and which gives it it’s common name.
- The time of year when you notice symptoms of a problem can be an important aid in determining what the cause of the problem might be. The onset of both biotic and abiotic problems tend to be tied to climactic conditions at certain times of the year, because of changes in temperature and moisture. These changes influence the life cycle of pest and disease organisms, and also the growth stage of the plant in question so paying attention to the time when symptoms appear can really help in diagnosis.
- An understanding of the basic characteristics of climate in your area is critical to understanding both the biotic and abiotic challenges plants in the area will face. Plant growth and pest and pathogen development are typically related and are profoundly dependent on climate. So bear in mind climatological factors like high and low temperature, rainfall amounts and the rainfall distribution through the year as well as other weather phenomena in your area.
- The other thing to keep in mind, of course, is how the plant (or plants) is supposed to look at the time of year that you are concerned about it.
- One type if injury that is common in temperate climates is cold injury to plants from low temperatures during the winter. Cold injury symptoms can vary widely depending on the plant, so a knowledge of the characteristics of the plant in question and the temperatures the previous winter is important. Also, the symptoms can show up immediately after the cold event occurs, or they may take time to develop, but generally any period of warm temperatures in early spring will bring on the symptoms. The photo shows a rosemary plant in April. This is a common landscape plant in western Oregon, however the various cultivars of the plant vary significantly in cold hardiness. Cold injury on these plants generally shows up as a patchwork of dieback on shoots, from which the plant will often recover with time. The previous winter, temperatures in the area had dropped below 10 degrees fahrenheit, cold enough to cause injury to this plant. Knowledge of the characteristics of the plant, the time of symptom development and knowledge of weather events all help in determining the cause of this problem.
- Cold injury is not the only type of problem that may surface early in the year. The photo shows a detached leaf from an ornamental Ash tree which is deformed by an infection by the fungal disease anthracnose. This is a fairly common problem in western Oregon, where the climate is quite rainy in the spring at the time these trees are leafing out and early shoot growth is occurring. The combination of continual moisture on leaf surfaces, and the young tender leaves means that the potential for infections is high. The more rain that is received during this time then the more severe the infections tend to be. In this climate, this pattern of rain during early plant growth provides opportunities for problems with fungal or bacterial disease problems on lots of different plants and so it is not uncommon to see these problems relatively early in the year. The amount of rain that is received declines drastically after April in the region, so it is unusual to see disease problems like this develop after this time. The lack of moisture serves as a natural control for these types of disease problems. In areas where rainfall is more evenly distributed throughout the year, the possibility exists that problems like this could continue into the summer months.
- Perhaps the problem on the plant appears later in the year. The photo above shows a row of Viburnum tinus against a south-facing wall in Corvallis, OR. The photo itself provides quite a bit of information which would help diagnose the problem. The population of the plant is about 15 individuals. Just looking at the photo, they all seem similarly affected by whatever the problem is. In looking at a specific plant (click) the problem is browning of the upper foliage and some tip dieback on the uppermost shoots (click). This problem occurred simultaneously on all these plants in summer. The pattern in the population immediately makes one suspect an abiotic cause. Also, the pattern on the individual plants is uniform as it is the uppermost foliage that is affected. Although Viburnum tinus is a species of Viburnum that is quite tolerant of heat and drought, an uncommonly hot stretch of several days preceded the injury to these plants. Also, they are growing immediately adjacent to a very warm brick wall with a reflective concrete base. As in the case of the rosemary sample, a little bit of additional information about the plant, time of symptom development and weather conditions helped in determining the cause.
- In a lot of cases, the symptoms will show up immediately after some specific environmental or cultural operation. Symptoms of freeze damage or sunburn can often show up immediately, or they may take time to develop. It depends on the plant in question and the severity and duration of the stress in question. Sometimes, the symptoms show up so soon after an event that they can often be quickly correlated with it. The photo shows a field of wheat and on the left side, the plants are showing definite chlorosis. Notice also the very distinct line between affected and unaffected plants. The pattern in this case is definitely uniform, and the cause is damage by some residual herbicide in the spray tank. Looking closely at the leaves on affected plants (click), the chlorosis is visible and it too takes on a uniform appearance. Patterns of damage like this are often characteristic of chemical injury to plants and this is no exception.
- When we are attempting to determine the cause of a plant problem, we often only see the plant at a single moment in time. Learning more about the time-development of the symptoms can be critical to determining the cause of the problem. If you are observing the plant for the first time, you may need to rely on others to provide you with information on how the plant has appeared in the past. What you are looking for is evidence that the problem has visibly worsened over a period of time, or that they have remained essentially unchanged, or that they have improved. Each of these possibilities gives further clues as to the potential cause.
- A classic pattern for a pest or disease problem in a population of plants, or within a single plant, is for the problem to appear in part of the population and then spread over time to other parts. Over time, then, these problems tend to become worse. An example of this is the spread of Phytophthora root rot in the population of Port-Orford Cedar in the photographs above. These photographs were taken over a 2 and a half year period. This species of conifer is very sensitive to the pathogen, which is soil-dwelling and infects and kills the roots of the tree, eventually causing death. In the earliest photo, discoloration of the foliage is apparent on two trees. A few months later, (click) these trees are predominately brown and dead, and a patchwork of foliar discoloration is evident in the hedge. The next photo (click) shows additional trees displaying dieback and the final photo (click) shows that the majority of the center of the hedge has died.
- The flip side of the situation just described is where the problem actually improves over time. In the photo is a section of a young aspen tree. Aspen is a deciduous shade tree and the photo was taken in June. Since it is deciduous, we know that all of the leaves present are from the current growing season. Also, we know that the youngest foliage is towards the tip of the shoots, and the older leaves from this year are towards the base. In looking at the foliage, you can see that towards the base of the shoots (click) there is evidence of chlorosis and browning on the edges and tips of the leaves. In fact, most of the leaves at the base seem to be similarly affected, which is suggestive of a uniform pattern of damage. When you look at the younger leaves neat the shoot tips (click x2), none of this damage is present and the foliage looks perfectly healthy. Whatever affected the plant, in other words, appeared to have occurred at some time in the past, and all subsequent growth is not showing symptoms. This type of pattern is strongly suggestive of some sort of cultural or environmental factor which occurred suddenly in the past and only caused damage to the foliage present on the plant at that time.
- Occasionally, you get situations where there are apparent symptoms of a problem which neither improve nor get worse over time. The first thing to check in these types of situations is that the “problem” is not simply a characteristic of the plant or population in question. The rose flowers depicted in the photo have white blotches distributed erratically over the petals. Although to some people it might look odd, it’s a cultivar of rose specifically developed and sold as a variegated flower.
- Chronic cultural problems are most commonly found in long-term perennial plants found in landscapes or in perennial agricultural cropping systems. With time the plant may in fact begin a slow but steady decline. With these problems the inclination is often to look for some sort of disease or insect pest problem but first ensure that the cultural or environmental conditions necessary for good growth of the plant are present. The photo shows a Rhododendron plant placed on the south side of building, partly under the cover of an overhanging part of the building that shades the plant on the left (building) side of the shrub. The plant is visibly more chlorotic on the right (sunny) side than on the left, shady side. But the plant overall appears to be growing in a substandard soil based on it’s weak growth, lack of foliage and chlorotic overall look. The next photo (click) was taken about two years later and shows the chlorosis continuing to develop. The photo after that (click) was taken another two years later and shows the plant in further decline. Although it’s possible that disease has begun to play a role in the decline of the plant, the symptoms early on pointed toward poor soil or other cultural problems. This is worth keeping in mind when looking at symptoms of plant problems over time.
- A critical part of determining what the cause of a plant problem is finding actual evidence of a specific pathogen or pest known to cause problems on the plant you are dealing with. Before looking into what to look for, it’s important to consider the difference between the symptoms that the plant will display when it is under stress, and the signs that point to a specific cause of the problem. These two terms refer to very different types of evidence of a problem, and the importance of this distinction is that for a given group of symptoms on a plant, there may be several potential causes. Differentiating between these various symptoms and determining the real cause of the problem requires finding signs of a particular pest, assuming a pest or disease is responsible for the problem. (Click) If the cause of the problem is some sort of abiotic problem like the sunburn evident on the foliage of this Rhododendron, then of course there won’t be signs of a pest since it isn’t a pest or disease problem. Because of this, even the absence of signs is helpful in determining the cause of a problem.
- Symptoms are reactions by the plant to the stress or stresses that may be affecting it. Plants respond in a lot of different ways to stress, as you can see by the long but still only partial list. In the photo is a common stress reaction, which is wilting of the cucumber plant. Simply by observing this reaction, we would not immediately know the cause of the wilting, which could be the result of several potential causes. Wilting can be the result of inadequate irrigation, compacted soil, physical damage to the main stems of the plant by an array of causes, or root rot caused by one of several potential disease organisms. To distinguish between these causes, we would need to look closer at the plant find specific signs of one or the other causes, which might ultimately require digging up the plant to inspect the roots.
- Discoloration of the foliage can take a number of forms. As we’ve already seen, in some cases it is simply a characteristic of some plants, which show different colors at different times of the year. The foliage may also discolor because of a number of stresses, including nutrient deficiency. The holly in the photo may be suffering from nitrogen deficiency, which will often result in chlorosis on leaves on parts of the plant.
- Leaf spots refer to necrotic lesions that show up on the foliage of plants. Leaf spots have many possible causes, both biotic and abiotic. In some cases leaf spots develop because the plant is under some kind of stress. They can also be caused by an array of fungi, and in some cases, though not all, definite signs of the causal organism can be distinguished within the spots themselves.
- Leaves and other plant parts may also develop irregular growth and shapes due to various causes. These types of irregularities typically show up on current season’s growth, because it is generally the softest growth on thev plant and therefore the most vulnerable to distortion. The leaves in the top part of this photo show distortion due to exposure to a phenoxy herbicide, which are commonly used for broad-leaved weed control in landscapes and agricultural situations. The normal appearance of the foliage is below. Some formulations of these can be volatile under warm and windy conditions and can move from the site of application to non-target plants, which is presumably how the foliage on this redbud was affected.
- Feeding injury by these bugs is noticeably worse on one side of the fruit than the other, quite possibly the injured side is the sun-exposed side of the fruit, therefore warmer and preferred by the bugs?
- Defoliation is another common symptom of plant stress. The photo shows a hedge of Photinia which has suffered major defoliation because of the fungal disease referred to as simply as leaf spot. As the inset shows (click), the disease causes small lesions on the foliage, which over time may coalesce and cause major leaf drop. This type of defoliation that indicates a genuine problem needs to be distinguished from normal leaf loss from deciduous and evergreen plants. In other words, make sure whatever is happening is not “normal”. Obviously deciduous trees lose their foliage in the fall (click), but both coniferous and broadleaved evergreen plants lose leaves as well, often throughout the year (click). And for those that live in climates with distinct periods of drought during the year, plants may respond to this by defoliating during that period of the year to avoid water stress. An example is plants from mediterranean regions, which often defoliate in summer when there is no rain (click) and leaf out again with the beginning of fall rains.
- Galls refer to swelling of plant tissues, which is often accompanied by discoloration and other symptoms of abnormal growth. Galls can occur in a multitude of forms, depending on the host plant, the tissue involved and the cause. Galls can occur on stem tissue anywhere on the plant. In the photo the gall is on the trunk of the cherry. In other cases (click) galls can occur on leaf tissue, as on this oak leaf.
- Cankers are constrictions of stem growth on plants caused by a reduction in growth of that section of the stem. Because of the reduction in growth, they show up as a depression in the stem. In the photo, the limb on this Red Alder is discolored and sunken in three distinct areas (click). The cankers are symptoms of some kind of undetermined fungal disease.
- Dieback of plant parts can show up in a multitude of ways. This example is on peach and visible in the photo is both dieback of the shoots at several nodes (click), as well as a canker evident along two sections of the stem (click). The presence of multiple symptoms on the plant may point strongly to a specific problem known to produce more than one symptom, or it might indicate more than one problem. In this case, it’s possible that the peach is affected by the fungal disease brown rot, which can produce both dieback and cankers on stem tissues.
- Rots are often associated with fruits or other edible portions of plants, although it is a broad-based term and of course vegetative parts of plants can also rot. Roots are the vegetative parts most often thought of that are susceptible to rots, problems which are often associated with excessively wet soils.
- Plant decline is a sort of catch-all phrase that indicates that the entire plant is failing to thrive. The term implies that rather than simply die outright, that instead the plant grows poorly and may display multiple symptoms of stress over a period of time. In the photo, a kousa dogwood has several limbs with dieback and little foliage in general. New growth, where it is present, is very restricted.
- As mentioned before, stress can cause plants to react in all sorts of ways and there may be more than one cause for a specific symptom on a plant. In many cases, you will be dealing with a cultural or environmental problem and these types of abiotic problems do not involve pests or pathogens that will often leave some evidence of their presence. However, where a biotic cause for a problem is involved, they will often leave signs of their presence. Looking for and finding these signs of a specific pest is critical to diagnosing the problem and developing a plan to deal with it. Sometimes signs are obvious, and sometimes they are much more subtle. The photo above shows a very obvious sign of a problem, in this case on Gaoldenchain tree. A portion of the plant canopy is distorted, which is a symptom of the problem. Closer examination (click) shows masses of aphids feeding on the twigs of the plant. A further sign of the problem is the shiny deposits (click) on the foliage, which is honeydew exuded by the aphids. Keep in mind this important distinction between symptoms and signs when looking at any plant problem
- Remember that as we look for signs of some biotic cause for the plant problem, we are looking for signs of organisms known to be or likely to be a pest or pathogen of that plant. Growing as they do out in gardens or fields, plants play host to lots of different insects, mites and other organisms that are not at all harmful to them. The presence of all these non-pathogenic organisms on the plants is actually a sign of a healthy functioning ecosystem. The photo above shows a crane fly resting on an apple leaf. Although crane fly is an occasional pest of lawns, and can be quite damaging, it is certainly not a pest of apple. Although this might be an extreme example, it’s a reminder that when we are scouting the plants for signs of a pest, we are looking for pests likely to cause whatever symptoms we see.
- The difference between symtoms and signs of a plant disease is illustrated by this example on the stems of sunflower. The base of the stem is discolored, and a close look reveals that the tissue is sunken in the discolored areas, in a canker (click). The canker itself is a symptom of the problem, but growing in the canker on one of the stems is a cottony mycelium of a fungus (click) which causes sclerotinia wilt. The cottony growth positively identifies sclerotinia as the pathogen responsible for the canker and the wilt that was affecting the sunflower plants.
- In some cases, in addition to the dieback evident on the plant there will be definitive signs of a specific pathogen which positively identify it as the source of the problem. We’ll go into greater detail about the difference between symptoms on the plant and actual signs of a pest or pathogen later on in the course. In the photo is the trunk of a Silk Tree which was injured by cold weather and subsequently failed to leaf out in the spring. The plant was not immediately removed and as the growing season progressed these raised orange structures appeared on the trunk. These are the spore-bearing structures of Nectria canker, a fungal disease which had colonized the winter-damaged stem tissues.
- In the case of plant disease organisms, in many case you may not see the mycelium or “body” of the fungus on plant tissue, as this is often restricted to growing within plant tissues. Instead, what you will see is the fruiting structures of the fungus, whose job is to produce spores to spread the disease. These may take a wide array of different forms, depending on the disease and the host plant. In the photo is an apple tree in Missouri which has orange-red lesions on the upper surface of the leaf. Underneath these lesions on the lower leaf surface are the spore-producing structure of a fungal disease known as rust. The specific disease may be cedar-apple rust, called this because like may rust diseases, it requires two host plants to complete it’s life cycle. The spore-producing structures on the underside of the leaf are called aecia and are characteristic of rust on apple.
- Rust diseases like the one on apple may require two host plants, and so the disease is often named for these plants. In Oregon, a similar rust disease exists which causes problems on apple and the alternate host plant is Incense cedar. A different type of spore structure known as telia develop in the spring on this cedar, and when it begins to rain, the orange jelly-like deposits form on the foliage. Spores from these deposits are spread to apple and other related host plants where they cause leaf spots and ultimately the spore-producing structure seen in the previous slide to complete the life cycle.
- Other plant diseases also produce signs in the form of distinctive fruiting structures signs that positively identify them. These will often be located within lesions on the leaves, stems flowers, fruit or other parts of the plant. This photo shows a bigleaf maple leaf, which has an irregular pattern of brown spots on the leaves. A close look at the spots (click) reveals small, black tarlike structures clustered within each spot. These are called stroma and are the spore-bearing structure of this disease.
- The preceding examples illustrated examples of fungal diseases which produce visible signs as well as symptoms on host plants. The presence of these signs greatly facilitates diagnosis of the cause of the problem. However, not all plant diseases produce visible signs, not even all fungal diseases. Some plant diseases are caused by organisms so small that they cannot be seen with the naked eye, and sometimes can’t be seen even with the aid of a dissecting scope. As a result, visible signs of the pathogen cannot be seen, which inhibits diagnosis. Some examples of diseases which are caused by microscopic pathogens include those caused by bacterial and virus pathogens. In some cases, symptoms produced by the pathogen may be so distinctive that it can be surmised to be the cause. In many instances however, a positive identification of the cause requires a laboratory isolation of the pathogen.
- In the case of insect pests, then the most compelling sign of a particular pest is of course the pest itself. In the photo is an apple tree showing a classic example of the difference between symptom and sign with insect pests. The leaves in many cases in the tree have rolled-under edges, a symptom that could be caused by various environmental, disease or other causes. Only upon opening up a curled leaf (click) do we find direct evidence of the cause, an insect pest referred to commonly as a leafroller (click) of which there are several species known to be pests of apple.
- This photo shows a Rhododendron with very evident stippling on the upper leaf surface. This type of damage is symptomatic of an insect pest with piercing-sucking mouthparts (click). The sign of the problem is found on the underside of the leaves, where a colony of Azalea Lace Bug is found. This insect has become a serious pest of both Azalea and Rhododendron in the Willamette Valley since first being found in 2009.
- Other insects find creative ways to protect themselves and these efforts serve as useful signs enabling us to diagnose the pest. Spittle bugs are found on a wide array of plants and are easily identified by the frothy mass surrounding the nymphs. The spittle mass is thought to protect the nymphs from predators. These insects do only minor damage to plants although they can distort new growth to some degree.
- If you are not seeing the insect itself, then there may be indirect evidence pointing to a specific pest. In the photo is a planting of Viburnum davidii, a popular evergreen groundcover. The edges of the leaves have characteristic notches cut out of their edges, a sign of feeding damage by an adult root weevil. The larvae of the weevil feeds in the soil on the root system of the plant causing further damage. It’s helpful that this Viburnum is known to be a host to root weevils. However, there are several different root weevil insect pests, so the actual species of root weevil responsible for this damage is not immediately clear. Ts would be very helpful to know, as the life cycles of these root weevils are not the same and management techniques may well be different.
- A large number of insect pests cause damage to trees and shrubs by boring under the bark and feeding on vascular tissues of the plant. Such damage can cause wilting and dieback of parts of the plant distal to the damage. This damage often is evident by an inspection of the exterior surface of the plant. In this example, the terminal growth of the Blue Spruce was wilting and dieing. Following removal from the plant, the terminal growth was found to be riddled by small holes (click) created b y the feeding activity of the White Pine Weevil, a pest of both White Pine and Spruce.
- Often feeding damage on a plant is accompanied by the presence of frass. The foliage of the apple tree in the photo has black specks that are the frass of the Apple-and-thorn skeletonizer.
- The shiny silver trails depicted on the concrete sidewalk are indicative of slugs and are also found on plants on which they have been feeding.
- The small holes, about 1” across in the flower bed above were created by voles. Vole burrows can be distinguished from moles or gophers by the lack of mounds and are smaller than those created by ground squirrels. Their tunneling activity around plants is similarly characteristic.
- With some pest problems, symptoms are readily visible but the signs of the causal agent are not. In some cases, this is because the causal agent is too small to be seen with the eye, even with magnification. Such is the case with disease problems caused by virus or bacteria. In both cases these are microscopic in size and cannot be seen without high levels of magnification. Often problems like these will require a lab analysis to definitively establish the cause of the problem. In some cases, the symptoms are so distinctive that a reasonable conclusion as to the cause can be determined. The problem in the photo is raspberry bushy dwarf virus, which causes chlorosis of the leaves on some raspberries and also causes poor fruit set, resulting in what are known as “crumbly” fruit.
- Another type of disease problem where the causal agent is too tiny to be seen is bacterial diseases. The Cherry tree in the photo has extensive dieback, probably because of Bacterial Canker caused by Pseudomonas syringae. The dieback is typical of the disease however other disease problems can cause dieback in cherry as well. Bacteria are too small to be seen without magnification, so other symptoms characteristic of this disease would be required to collectively conclude that this disease was the cause of the problem. This might include the presence of cankers and gumming (click) on stem sections, along with other symptoms known to be associated with the disease.
- When you are looking at an afflicted plant, remember the importance of signs as a guide to specific pathogens. The reality is that symptoms of stress show up commonly on plants and have many different causes. Sometimes these symptoms look amazing like they should be caused by pathogens but are not associated with one. The pear in the photo has leaf spots that look like they should be caused by a fungal disease, but there were no obvious signs of a specific pathogen, and even after a lab test, no pathogen was recovered. It appears as though the spots were the result of some kind of environmental stress. Abiotic factors are responsible for much of the symptoms of stress o plants and the next several modules explore the various causes of cultural and environmental stress.
- Indigo Rose tomato plant with immature fruit
- Normal tomato root system
- This form is copied and available at the Desk. The purpose of the form is to assist the MG volunteer in gathering basic information on the characteristics of a plant problem, the growing environment and cultural practices that will assist in solving the problem. The questions on the form correspond roughly to the questions to ask in plant problem diagnosis later in the presentation.