Common Evergreen & Tree Diseases- K. Korus
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Common Evergreen & Tree Diseases- K. Korus



Kevin's presentation about Common Evergreen & Tree Diseases from 3-19-14

Kevin's presentation about Common Evergreen & Tree Diseases from 3-19-14



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Common Evergreen & Tree Diseases- K. Korus Common Evergreen & Tree Diseases- K. Korus Document Transcript

  • 3/19/2014 1 Common Evergreen Tree Diseases Diplodia / Sphaeropsis Tip Blight Sphaeropsis Tip Blight (Diplodia)  Austrian, Scotch, red, ponderosa and mugo pine  Spores overwinter on infected needles, needle sheaths and cones  Rain and high humidity are required for spore germination Images courtesy of University of Nebraska SphaeropsisTip Blight (Diplodia) Control  Avoid overcrowding  Protective fungicide sprays  Two applications  Third week of April - first week of May  Bordeaux mixture Image courtesy of University of Nebraska Dothistroma Needle Blight  Austrian & ponderosa pine  Needles infected by fungal spores as they emerge in spring  Brown to reddish brown spots begin to appear in early fallImage courtesy of University of Nebraska Dothistroma
  • 3/19/2014 2 Dothistroma Needle Blight Control  Plant resistant evergreen varieties  Avoid overcrowding trees  Maintain good air circulation  Protective fungicide sprays  Bordeaux Rhizosphaera Needle Cast Rhizosphaera Needle Cast  Colorado blue spruce – susceptible; Norway spruce – somewhat resistant  Purple brown needles with black fruiting bodies of fungus associated with stomata in rows on needles Rhizosphaera Needle Cast Control  Plant resistant varieties  Reduce stress on trees  Water and mulch during dry weather  Preventative fungicides when new growth is ½ - 2 inches  Repeat in 3-4 weeks Cytospora Canker of Spruce Cytospora Canker
  • 3/19/2014 3 Cytospora Canker of Pine Cytospora Canker of Pine Stroma Cytospora Pitch Cytospora Canker of Concolor Fir Cytospora Canker of Concolor Fir Image courtesy of Sarah Browning, University of Nebraska Cooperative Extension PineWilt  Scotch pine  Also Austrian and sometimes white pine  Older tree, at least 10 yrs  Rapid decline of tree  Causal organism  Pinewood nematode  Vector  Pine Sawyer beetle Nematodes enter feeding wounds Susceptible host Pine sawyer beetles lay eggs in bark of dying trees. Pine Wilt Disease Cycle Resistant host: Transmitted nematodes die Nematodes feed on blue stain fungi Nematodes attach to pupae before they emerge Bark beetle galleries
  • 3/19/2014 4 PineWilt  Currently no chemicals are recommended to control either the beetle vector or the nematode  Diseased trees should be removed by end of April, which is before the beetles become active and could move the nematode from infested to non-infested trees  Trees should be burned or buried Winter Injury *Abiotic Diseases of Hardwoods / DeciduousTrees Anthracnose  Sycamore, ash, oak, maple, walnut  Also poplar  Host specific fungi  Causes leaf spot or leaf blight (typically along leaf veins)  Twig and shoot Oak Anthracnose Ash Anthracnose
  • 3/19/2014 5 Anthracnose  Fungi overwinter on infected twigs or small branches  Symptoms appear following cool, wet weather in spring  Leaf or shoot blight may appear suddenly after a rain Anthracnose Control  Plant resistant species  Rake & destroy fallen leaves  Prune out dead or infected branches  Mulch & water during dry periods  Protective fungicide spray Apple Scab  Favored by wet, humid weather  Olive to greenish-black lesions on leaves, petioles and fruits  Fruit lesions enlarge and become cracked & scabby Image courtesy of University of Nebraska Apple Scab Apple Scab Control  Plant resistant varieties  Rake & remove infected leaves  Protective fungicide spray Image courtesy of University of Nebraska Upper leaf surface Lower leaf surface Aecial spores Telial spores Cedar-apple rust
  • 3/19/2014 6 Cedar-Apple Rust  Apple, crabapple, hawthorn  Spore production & release favored by wet weather  Spores blown from juniper host to apple Cedar-Apple Rust  Fruit lesions similar to leaf spots  Infected at blossom end  Decrease fruit size  Fruit distortion  Premature fruit drop Images courtesy of University of Nebraska Fire Blight  Apple, crabapple, pear, cotoneaster, hawthorn, firethorn, mountain ash, rose, quince, spirea, viburnum (limited)  Bacterial disease  Erwinia amylovora Courtesy Iowa State University Fire Blight  Bacteria overwinters at edge of cankers  Milky ooze from cankers contain hundreds of bacteria  Bacterial ooze spread by rain, wind and insects to the flowers Courtesy University of Nebraska Fire Blight  Blossoms wilt, shrivel and turn brown  Twigs form shepard’s crook at tip  Leaves wilt, then turn dark brown or black and remain attached to the tree Courtesy University of Nebraska Fire Blight  Sunken, smooth cankers develop on main branches and trunk  Cankers eventually become cracked
  • 3/19/2014 7 Fire Blight Control  Plant resistant varieties  Prune and discard infected branches  Prune only during the dormant season  Cut 6-12 inches below the visible canker  Apply fertilizers sparingly in spring  Protective sprays  Streptomycin or copper-based beginning at pink stage Courtesy University of Nebraska Dutch Elm Disease  American elm  Fungal disease transmitted by insect vector  Native bark elm beetle  European elm bark beetle Image courtesy North Dakota State University Dutch Elm Disease  Also can be spread through natural root grafts Image courtesy Colorado State University  Streaking of vascular tissue, characteristic symptom Dutch Elm Disease  Management  Remove dead trees  Prevent root grafts  Plant resistant elms  Injection of chemical fungicides to protect high value trees Thousand Canker of Walnut  Walnut twig beetle (Pityophthorus juglandis)  Cankers (Geosmithia sp and Fusarium solani) Thousand Canker of Walnut  Initial symptoms involve a yellowing and thinning of the upper crown  Progresses to include death of larger branches  Final stages – large areas of foliage may rapidly wilt  Trees often killed within 3 years after initial symptoms
  • 3/19/2014 8 Open Cankers Do Not Form  May see bark cracking around entrance holes, star shaped wounds at leaf scars, and staining on trunk, but these are not diagnostic Dr. Ned Tisserat Distribution of Black Walnut Management  Do not move fire wood  Currently no chemical control Oak Wilt  Fungal vascular disease  Causes wilting and browning of leaves  Brown discoloration or streaking in sapwood Oak Wilt Control  Management  Remove dead trees  Prevent root grafts  Injection of chemical fungicides to protect high value trees  Sample from partially wilted branches that have discolored sapwood to confirm disease
  • 3/19/2014 9 Sudden Oak Death Spread of Phytophthora ramorum Verticillium Wilt  Affects over 300 kinds of plants  Annuals & perennials  Trees & shrubs  Food & fiber plants  Caused by a soil-borne fungus  Attacks the plants vascular system Image courtesy Ned Tisserat, Kansas State University Research & Extension Verticillium Wilt  Microsclerotia  Resting structure  Survives in soil for several years  Fungal spores invade the plant though root wounds  Cool temperatures favor fungal developmentImage courtesy Ned Tisserat, Kansas State University Research & Extension Verticillium Wilt Control  Avoid planting susceptible plants in locations with a history of verticillium wilt  Remove infected branches  Burn infected wood debris Image courtesy Ned Tisserat, Kansas State University Research & Extension Ash rust  Dual Host Organism  Ash (white, green, black)  Cordgrass and Marsh grass
  • 3/19/2014 10 Ash rust disease cycle Teliospores Basidiospores Aeciospores Spermagonia Ash rust management  Cool wet spring  Serious damage occurs only after repeated infection  Fungicide application at bud break until full leaf emergance  Bayleton  Chlorothalonil  Myclobutanil  Propiconazole Stem Canker  Fungal—Coniothryium spp. and others  Enters wounds during wet or humid weather  Causes wilting foliage and twig dieback  Black spot infestations are easily invaded by canker fungus  Cut at least 5 inches below infection and disinfect tools  Spray with lime sulphur fungicide Cankers  A localized diseased area or lesion in the bark of a woody plant which often results in an open wound Canker Cankers  Nearly all canker pathogens are wound parasites  Death of bark and underlying cambium tissue is associated with a dead bud, branch stub, or twig, or with some type of mechanical injury
  • 3/19/2014 11 Cankers  Most cankers produce fruiting structures on newly killed wood.  Tendrils of Cytospora canker. Cankers  Identification is the key to management – good rule for basic disease management.  Often with cankers this is not the case, just need to know yes/no is canker present.Cytospora Canker of Douglas Fir Image courtesy of Sarah Browning, University of Nebraska Cooperative Extension Thyronectria Canker of Honeylocust  Consistently associated with trunk and stem wounds.  Wounds become resistant to infection between 7 to 14 days after wounding.  Trees under stress may be susceptible for longer periods. Conditions Favoring Cankers  Environmental stresses favor the development of most canker diseases.  Mechanical wounding provides entry sites for canker-causing pathogens.  Moisture after wounding (within one week) creates an environment favorable for infection. Thyronectria Canker of Honeylocust Image courtesy of Michigan State University Extension Conditions Favoring Cankers  Drought stress is NOT favorable for all cankers.  Drought reduces Thyronectria.  Drought favors Cytospora. Canker Management  Fungus readily infects wounded tissue but remains latent in the tree without causing symptoms – fungicide sprays cannot be effectively timed.  Wound dressings are not recommended.  Select the planting site carefully, avoiding drought prone sites. (Anticipate the future needs of the mature tree) Cytospora Canker of Douglas Fir Image courtesy of Sarah Browning, University of Nebraska Cooperative Extension
  • 3/19/2014 12 Canker Management  Remove dead trees and prune diseased branches.  Disinfect tools after each cut.  Prune in late winter or during dry periods to reduce the potential spread of the pathogen. Image courtesy Michigan State University Extension Diseases of Landscape Perennials Powdery Mildew  Superficial white or gray growth over the surface of leaves, stems, fruits & flowers  Host specific fungi  Favored by  Moderate temperatures  High humidity  Poor air circulation Powdery Mildew  Spaherotheca pannosa var. rosae fungi develop wind- borne spores  Low rainfall plus 70°–80°  Low daytime humidity,high nighttime humidity  Depletes nutrients Powdery Mildew Control  Plant resistant varieties  Rake & remove infected leaves  Improve air circulation  Increase sun exposure  Avoid overcrowding plants  Improve soil drainage  Protective fungicide sprays
  • 3/19/2014 13 Black Spot  Fungal—Diplocaron rosae  High humidity and wet foliage  Spores overwinter on infected tissue  Circular black spots with fringed margins, yellow around spots  Poor quality flowers; plant may die Black Spot Rose Rosette  Viral—maybe  Affects plants with R. multiflora in parentage  Wild, reddish growth  Spread by insect vector  Remove all infected plants Rose Rust Rose Rust  Yellow/brown spots on upper leaf surfaces, starting on lower leaves  Blotchy undersides  Plants lack vigor  Fungi (Phragmidium spp.) develop wind-borne spores  Moisture/moderate temperatures (55°-75°)
  • 3/19/2014 14 Black Knot Crown Gall Crown Gall  Bacterium (Agrobacterium tumefaciens) in soil; often imported on tools  Enters through wounds and secretes a compound causing rapid cell growth—galls  Disrupts flow of nutrients and water  Prune out galls and canes and disinfect Plant resistant varieties Crown, Root and Stem Rots  Most landscape perennials/annuals susceptible Crown, Root and Stem Rots  Many plants susceptible to crown, root and stem rots  Caused by many different types of Fungi and Bacteria Crown, Root and Stem Rots  Symptoms: ◦ Discoloration of stem, crown, roots ◦ Plants are wilted, flaccid ◦ Dark brown/black water soaked tissues ◦ Foul odor
  • 3/19/2014 15 Crown, Root and Stem Rots  Management: ◦ Plant resistant varieties ◦ Improve soil drainage ◦ Remove infected plants ◦ Chemical treatments involve soil drenches which are costly and need repeat applications Plant Health Management  Choose right, place right  Environment and spacing  Diversity  Be observant  Do you look or do you see?  Catch problems early  Minimize stress to maximize health QUESTIONS? Authors: Sarah Browning, Extension Educator Jennifer Chaky,Extension Educator Loren Giesler, Asst. Professor/Plant Pathology AmyTimmerman, Extension Educator Kevin Korus, Extension Educator TURF.UNL.EDU