Grow Your Own, Nevada! Summer 2013: What is Wrong with My Plant?


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  • Management Of Thrips In Greenhouse Crops Agdex#: 290/621 Publication Date: 09/03 Order#: 03-075 Last Reviewed: 08/09 History: Replaces OMAFRA Factsheet Pest Management of Thrips in Greenhouse Vegetables, Order No. 94-023 Written by: Graeme Murphy - Greenhouse Floriculture IPM Specialist/OMAFRA; Gillian Ferguson - Greenhouse Vegetable IPM Specialist/OMAFRA; and Les Shipp - Greenhouse Entomologist/ Agriculture and Agri-Food Canada Table of ContentsIntroductionManagement StrategiesMonitoringCultural ControlPhysical ControlBiological ControlChemical ControlRelated LinksIntroductionThrips are a major pest of greenhouse crops in Ontario. A number of thrips species are commonly found including western flower thrips (Frankliniellaoccidentalis), eastern flower thrips (Frankliniellatritici), onion thrips (Thripstabaci), and Echinothrips. However, the western flower thrips is the predominant species and the most difficult to control. See OMAFRA Factsheet Order No. 03-077, Biology of Thrips in Greenhouse Crops for a detailed description of the pest. Management StrategiesMonitoringMonitoring the population levels of western flower thrips is critical for successful pest management. In vegetable crops, begin monitoring during propagation and continue after transplanting. In floriculture crops, thrips can be present at damaging levels year-round, although populations are usually reduced during winter. Use commercially available blue or yellow sticky traps to monitor the population densities of adult thrips (Figure 1). Blue traps are more attractive to western flower thrips, although yellow traps are more attractive to other pests such as whiteflies and aphids. The choice depends on how many pests need to be monitored, the susceptibility of the crop to thrips and/or tospoviruses, and the need to detect thrips populations at low levels. Figure 1A. Blue sticky card.Figure 1B. Yellow sticky card.When setting up a monitoring program use 1 trap per 100-200 m2. The exact number will depend on the layout of the greenhouse. A large open range will require a lower total density of cards than a greenhouse made up of a number of smaller areas. Place the sticky cards in a grid pattern throughout the greenhouse. Check the traps weekly to record the average number of thrips per trap per week. Be aware that this is not an absolute measure of the population - it measures population trends, the increases and decreases in thrips numbers throughout the year. As you become more aware of how the numbers on sticky cards relate to the population in the crop, you can use the monitoring data to assist in making pest management decisions. There are precision-level sampling programs for monitoring adult western flower thrips on sweet pepper and cucumber. These sampling programs vary the number of samples taken according to the population level of the pest, and accurately predict the pest density to set precision levels. Contact an OMAFRA Greenhouse Pest Management Specialist or your IPM consultant for more detailed information before implementing your monitoring program. Cultural ControlSanitation is the first and most important step in implementing an effective pest management program. Effective sanitation reduces or even eliminates thrips as a pest problem. For example, in cut roses, removing all flower buds (including non-marketable flowers) can significantly reduce thrips populations in that crop. For more detailed information on implementing an effective sanitation program in greenhouse vegetables, see OMAFRA Factsheet, Order No. 94-029, Sanitation Recommendations For Management of Insect & Mite Pests of Greenhouse Vegetables. Cultural control measures also include maintaining a healthy crop and an optimal greenhouse environment (such as 80% RH) that would provide less favourable conditions for a rapid increase in population densities of thrips.Physical ControlInsect exclusion screening restricts the movement into the greenhouse of many common greenhouse crop pests including thrips, removing an important variable from a grower's pest management program. The influx of pests from outside can overwhelm an IPM program, making it difficult for a grower to plan ahead. For more information on screening, see the OMAFRA Factsheet Order No. 00-021, Screening of Greenhouses for Insect Exclusion. Biological ControlBiological control of thrips is used more frequently and more successfully in greenhouse vegetables than in floriculture production. However, an increasing number of flower growers are also using this strategy with success. Predatory mites (Neoseiulus (=Amblyseius) cucumeris, Iphesius (=Amblyseius) degenerans and Hypoaspis spp.) and minute pirate bugs (Oriusinsidiosus) provide effective biological control of thrips. N. cucumeris is the most extensively used of the predatory mites (Figure 2). N. cucumeris controls western flower thrips by feeding only on the first instar larvae. As such, it takes a number of weeks for the impact of this predator to be seen in the greenhouse, and it is unlikely that it will completely eliminate thrips populations. The life cycle for N. cucumeris is completed in approximately 10 days at 20°C and 6 days at 25°C. Figure 2. Adult and egg of Neoseiuluscucumeris.Introduce predatory mites at the beginning of the crop or as soon as thrips are detected. Sanitation at the end and beginning of a cropping season is extremely important and will delay any thrips infestation until the biological control agents can be effective. Regular introductions of N. cucumeris are necessary, either by dispersing bran on plants or growing medium, or by hanging a bran bag rearing system on plants (Figure 3). The bag system provides a continuous release of mites to the plant and should be replaced monthly. The number of introductions of N. cucumeris depends on the crop and level of thrips infestation (contact an OMAFRA Greenhouse Pest Management Specialist or your IPM consultant). Control of the thrips should be achieved in 5-9 weeks. When using N. cucumeris, it is important to maintain at least 70% RH in the greenhouse and not to have used any persistent pesticides such as carbamates or synthetic pyrethroids for several months. Orius is effective in controlling thrips (Figure 4). Unlike N. cucumeris, Orius feeds on all stages and is often found in the flowers where it feeds on pollen as an alternative food source. Orius does not seem to be as effective in flower crops as it is in vegetables. Development time from egg to adult is 31 days at 20°C and 19 days at 25°C. Orius enters reproductive diapause when daylength is less than 12 hours per day. Thus, Orius is only effective as a biological control agent from March to September.Figure 3A. Introduction of predatory mites directly onto the plant.Figure 3B. Introduction of predatory mites using the bag rearing system.Figure 3C. Introduction of predatory mites onto the growing medium from where they will move onto the foliage of young plants.Figure 4. Adult Oriuspreying on western flower thrips.The introduction rate for cucumber and sweet pepper is 0.5-1 Orius per plant when the pest level is low. One or two releases are usually sufficient to provide thrips control in approximately 3-5 weeks. Orius are introduced as adults in several locations and allowed to naturally disperse by flying throughout the greenhouse. Flower sampling is the best method to monitor the presence of Orius. Orius at 2.5 per cucumber plant also provides effective control in 3-6 weeks when the population levels of thrips are high (5-9 per flower). Iphesiusdegenerans (Figure 5) differs from N. cucumeris in appearance and in being able to tolerate less humid conditions. It is dark, very agile and reproduces very well on pollen. Therefore it performs best in crops with a pollen source, e.g. greenhouse peppers, and is unlikely to be the best option for floricultural crops. It can be reared in the greenhouse on castor bean plants (which produce large amounts of pollen) that may be used as release points for the predator within the greenhouse. Figure 5.Iphesiusdegenerans.Hypoaspis is a soil-dwelling predatory mite that feeds on a variety of soil organisms, including thrips pupae (Figure 6). Apply as a once-only application to the growing medium (e.g., rockwool, peat mixes) at the beginning of the crop. It is difficult to determine the exact impact of Hypoaspis on a thrips population, but it is better used in combination with other predators and is unlikely to provide sufficient control on its own. Figure 6. The predatory mite, Hypoaspis. Chemical ControlChemical control of western flower thrips can be difficult. They are resistant to most pesticides and feed deep within the flower head or on developing leaves. This makes them a difficult target for insecticides, so thorough coverage is essential. General recommendations regarding pesticide use for thrips control are as follows: At the action threshold (when thrips population levels dictate spraying to prevent economically damaging numbers from appearing), spray 4-5 days apart for 3 consecutive applications.Rotate chemical classes and use a single chemical class only for the duration of the thrips' life cycle. This generally means using a different class every 2-3 weeks depending on time of year. Generation times are longer at cooler temperatures.Apply pesticides in early morning or late afternoon, when flight activity of thrips is at a peak. This increases exposure of the thrips to the pesticides.
  • We’re all familiar with earwigs, but controlling these shy, nighttime insects can be difficult. They feed on a wide variety of living plant material, including vegetable fruits and foliage. Recently earwigs have been observed in the heads of leafy greens, which would warrant control. They can also feed on the soft flesh of developing sweet corn.Keep in mind that earwigs are also beneficial predators of mites and soft-bodied insects and insect eggs, so they are not all bad.In the home garden, trapping earwigs is an alternative to insecticides. Use tuna cans filled with 1/2-inch of fish or vegetable oil or bacon grease. Dump out trapped insects and refill can regularly. Rolled up newspaper or corrugated cardboard will also attract insects for hiding during the day. Empty into a can of soapy water regularly.Treatment: If control close to harvest is warranted, products with insecticidal soap or pyrethrin have a PHI of 12-24 hours.
  • Management (Back to Top)Sampling. Several methods for population assessment have been studied, and collecting puparia in trays placed beneath plants was recommended by Johnson et al. (1980b) as a labor-saving technique. Zehnder and Trumble (1984) used yellow sticky traps to monitor adults, and reported that Liriomyzasativae flies were more active at the middle plant height of tomatoes, while Liriomyzatrifolii was more active at low plant height. They also confirmed the value of pupal counts for prediction of adult numbers two weeks later. Yellow sticky traps, however, have the advantage of being able to quickly detect invasion of a field by adults from surrounding areas. Sequential sampling plans were developed by Zehnder and Trumble (1985). Insecticides. Foliar application of insecticides is often frequent in susceptible crops Insecticide susceptibility varies greatly both spatially and temporally. Many organophosphate and carbamate insecticides are no longer effective. Insecticides are disruptive to naturally occurring biological control agents, and leafminer outbreaks are sometimes reported to follow chemical insecticide treatment for other insects. Insect Management Guide for vegetablesCultural practices. Some crops vary in susceptibility to leaf mining. This has been noted, for example, in cultivars of tomato, cucumber, cantaloupe, and beans (Hanna et al. 1987). However, the differences tend to be moderate, and not adequate for reliable protection. Nitrogen level and reflective mulches are sometimes said to influence leafminer populations, but responses have not been consistent (Chalfant et al. 1977, Hanna et al. 1987). Placement of row covers over cantaloupe has been reported to prevent damage by leafminer (Orozco-Santos et al. 1995). The same study evaluated the benefits of transparent polyethylene mulch, and found no reduction in leafminer populations. Sometimes crops are invaded when adjacent crops are especially suitable, as was reported by Sharma et al. (1980) in California, where cotton was an important source of invaders. Weeds are a source of flies (Parkman et al. 1989), but also a source of parasitoids.
  • Grow Your Own, Nevada! Summer 2013: What is Wrong with My Plant?

    1. 1. What’s wrong with my plant? How to Diagnose Plant problems Wendy Hanson Mazet University of Nevada Cooperative Extension
    2. 2. First - What is the problem? Is there a pest present? Anything or anyone that is detrimental to your garden is a pest  destroys crops & structures  poses health threats to family or pets  reduces aesthetic value of your property
    3. 3. Anticipates and prevents damage Uses several tactics in combination Improves effectiveness, reduces side effects Relies on identification, measurement, assessment, and knowledge Integrated Pest Management IPM: a balanced, tactical approach
    4. 4. An IPM Year
    5. 5. How to have success Six Key Steps  Observation  Early Detection  Correct Identification of insect or pest or issue  Education / research  Select appropriate control or action  Proper application
    6. 6. What is causing the problem?  Biotic  Living Agents  Viruses  Fungi  Bacteria  Abiotic  Non-Living Agents  Soil issues  Nutrient Deficiencies  Temperature  Wind  Water  Sun  Shade
    7. 7. Biotic  Signs of Fungal Diseases  Visible organism  Rust pustules  Mycelial groth (fuzzy spots)  Spores  Black fungal bodies  Bacterial diseases enter through wounds  Symptoms  lesions,  Wilt  Discoloration of leaves  Galls  Slimy wet areas or roots
    8. 8. Biotic cont.  Virus  Virus infects plant tissue and cells  Symptoms:  Mottling  Mosaic color patterns  Purple coloring  Stunting  Distortion  Insects, mites, fungi or nematodes often are the carrier of viruses and transmit the virus.
    9. 9. Powdery Mildew  Fungal Disease  Looks like talcum powder or flower dust on leaf tissue  Use of resistant varieties  Avoid poor air circulation  Over abundant shade  Avoid excessive overhead watering and night time foliar watering  Change the environment first, before turning to fungicides
    10. 10. Determine causes of plant damage  Environmental injury includes:  Temperature extremes: too hot, too cold  Lightning  Storm situations with hail, wind or tornado  Wind injury  Frost damage  Moisture extremes: too much, too little  Monitor the area since some environmental injuries can resemble other biotic or abiotic causes.  Abiotic causes of plant damage are non-living.  Generally are distributed uniformly across a plant or field and are repeated  Don’t spread or move with time  May be from mechanical factors such as cultivator injury; physical factors such as environment; or chemical factors such as pesticide or nutrient problems
    11. 11. Cucumber  Scenario:  2 p.m.  96 degrees Fahrenheit  Watered at 7 a.m. insects? disease? environmental? Where do you start?
    12. 12. Biotic vs. Insects  Identifying Insects  Symptoms may include tunnels in stalks or leaves, holes in leaves, chewed leaves, galls, leaf curling, speckling or separation of leaf tissue.  Biotic  Look for pattern  Mottling, mosaic or stippling or leathery leaves  Do not over head water in the evening hours  Take photos and bring in a sample for lab testing.
    13. 13. Control Tactics of insect damage Five Most Common  Mechanical  Cultural  Physical  Genetic  Chemical
    14. 14. Insects - Know Your Enemy:  Sucking Insects: Pierce and suck plant juices  Yellow or bronze discoloration of leaves and shoots  Wilting and curling of leaves and shoots  Aphids, whiteflies, mites (not true insects) feed near tip of young shoots and on undersides of leaves  Leafhoppers feed under leaf surfaces, and scale feed on leaves, stems, and shoots.  All feed in large groups except leafhoppers
    15. 15. Piercing Insects Control:  Keep plants healthy  Maintain a diverse habitat  Monitor garden daily, so when insect pests are found, control measures can be taken quickly.  hose plants off  insecticidal soap sprays  horticulture oils including Neem oil  Cover with garden blanket  Encourage Beneficial insects
    16. 16. Aphid • Small, soft bodied insects 1/10 inch long • Long mouth parts used to suck plant juices. • Cornicles are found on most species. • Found in many colors. • Most over-winter as eggs, hatch in spring. • Secrete honeydew. • Most abundant in cool spring and cool fall. • Ants may be present tending aphids.
    17. 17. NCCE Stink Bugs •5/8 inches long, bright green, brown with stripes, large body small head • When crush they stink! •Piercing/sucking mouth parts • stippling damage on leaf and stem tissue •Barrel like eggs laid on leaf and stem tissue
    18. 18. University of Minnesota Extension Squash Bugs •5/8 inches long, brown with stripes, large oblong body small head •Overwinter as adults •Piercing/sucking mouth parts • stippling damage on leaf and stem tissue •Eggs are rust to root- beer colored and found on the undersides of the leaf
    19. 19. Spider Mites •Very small •Not an insect. • Arachnid possessing 8 legs. •When spider mites feed on fruit can cause a silvery or bronzy sheen called russetting. •When populations are large a fine webbing may be seen on leaves and needles. •Prefer hot, dry and dusty environments.
    20. 20. Mites Cont. Several species of mites in our area.  Common is two-spotted spider mite  Found on outdoor plants, garden areas and houseplants.  Spruce spider mite  Found on Juniper, Spruce, and other needled-leaf evergreens.  Clover mite-pest of lawns and weedy areas  Occurs as periodic lawn pest, and nuisance in spring and Fall.
    21. 21.  Adults a wedge-shaped and about 1/8 inch long  Leafhoppers over-winter as eggs on twigs, or as adults in protected sites, such as bark crevices.  Very active – jumping, flying and running when disturbed.  Sucking mouthparts cause stippling, yellow to brown leaves.  Nymphs are considered more damaging than adults Leafhoppers
    22. 22.  Slender insects with fringed wings as adults  Less than 1/20 inch long  Feed within buds and furled leaves or in other enclosed parts of the plant  Thrips are poor fliers but can readily spread long distances by floating with the wind Thrips Orius insidiosus
    23. 23.  White Moths with powdery wings 1/10th inch in length • Eggs are typically laid on the newest leaves. • Piercing-sucking method of feeding produces stippling of leaves • Heavy feeding may wilt and stunt plants • Hosts, bean, cucumber, eggplant, lettuce, okra, potato, tomato, squash, and sweet potato. Whitefly
    24. 24. Chewing Insects Loopers, hornworms, leafrollers, cutworms are all larvae of butterflies and moths. Control:  Handpick larvae  Cover with garden blanket  Bacillus thuringiensis-Bt  Encourage Beneficial insects Cabbageworm Butterfly
    25. 25. Earworm • ½ inch to1 inch in length • Prefer cool damp places hiding in organic mulch, under bark, in garden debris • Feed on a variety of dead and living organisms, including insects, mites and shoots of plants. • Earwigs also feed on silks of corn, causing poor kernel development.
    26. 26. Miller Moth Army Cutworm •Smooth, gray-black with smooth skin •Can reach 1 ½ inches long •When disturbed they curl into a C shape •Caterpillars chew on stems and leaves •Adult is known “Miller Moth”
    27. 27. • 1 ¾ inches long • Light green to brownish black • Alternating light stripe running down the length of its body • Chews holes in leaves and fruit • Eggs laid on the silk • Adult is a moth and overwinters as a pupa Corn Earworm
    28. 28. Cabbage & Alfalfa looper •Loopers 1 to 1.5” •feed on leaves •Female can lay 200-350 eggs over a 12 day period – hatching occurs within 2 weeks •Larvae will feed 2 to 4 weeks •Note: plants can lose 20 to 25 percent of their leaf area without a reduction in yield
    29. 29. •Large green to brown caterpillars – up to 3-4 inches •Can defoliate a tomato within days •Adult is a sphinx moth – known as a hummingbird moth •Pupa overwinter in the soil Hornworm
    30. 30. Leafminers •Larvae a maggot or slug like and burrow between the two layers of tissue •Adult small slender-bodied, grayish, black-haired fly – ¼” long •Larvae will pupate in the top 3” of soil, but some will stay in the leaf itself •3 to 4 generations a year •Larvae over winter in the soil
    31. 31. The Good Guys – Naturally occurring predators Lady beetles Snake fly Green lacewing
    32. 32. University of Minnesota Extension –Karl Foord
    33. 33. Predators available for purchase  Convergent lady beetle  Spined soldier bug  Praying mantid eggs  Green Lacewing Eggs
    34. 34. Cracking  Tomatoes often start to crack during warm, rainy periods particularly following a lengthy dry spell.  Fruits crack by expanding too fast, usually when they are fully-size and beginning to color.  To avoid cracking:  select resistant varieties  keep soil moisture as even as possible  avoid excessive dryness or wetness through-out the growing season
    35. 35. Blossom End Rot  Physiological disorder that occurs on tomato, pepper, eggplant & summer squash.  On zucchini and other summer squash, the blossom end of the fruit begins to rot and within a short time the entire fruit has rotted.  Caused by a lack of calcium in the developing fruit. The deficiency typically occurs during high summer temperatures  No need to apply calcium to the soil.  Try to maintain an even moisture supply by watering  Uneven moisture supplies and excessive nitrogen can inhibit calcium uptake.
    36. 36. Catfacing  Characterized as unusual, and sometimes bizarre, swellings, streaks of scar tissue, caused by abnormal development of the tomato flower at blossom time.  Cool weather is believed to cause the flower problems.
    37. 37.  Summer Squash Fruit Abortion  Improper pollination of the flower  Encourage beneficial insects  Plant umbel flowers near squash plants
    38. 38. Sunburn/sunscald  Hot afternoon sun  When green or ripening tomatoes get too much sun exposure  The first symptom is a yellowish-white patch that appears on the side of the fruit facing the sun.  The area will enlarge as the fruit ripens and become grayish-white.  Maintain adequate foliage on the plants  Add additional shade if possible  Grow plants in tomato cages,
    39. 39. Voles •Also called meadow, field or pine mice •4 to 8.5 inches long •vary in color from brown to gray •Large colonies •Damage by voles can be reduced by : •habitat modification •exclusion •Repellents •Trapping •poison grain baits • /PESTNOTES/pn7439.html UC IPMMissouri Botanical Garden Curtis, B, D. Curtis, and W. Miller. 2009
    40. 40.  =/PMG/PESTNOTES/pn74161.html House & Deer Mouse •House Mouse •vary in color gray, light brown to black •Short hair, with small eyes and large ears •Life span 9 to 12 months •Deer Mouse •Two-tone, brown to grey on top with a white belly. Tail 50/50 tan and white •Start reproducing at 6 weeks of age •Prefer seeds, but will eat fruits, invertebrates and fungi
    41. 41. Woodrats Important Facts: •Also known as pack rats, bushy tailed wood re and trade rat •Active at night •Build stick dens on the ground or in trees •Herbivores, green vegetation, twigs and shoots •1 litter per year – litter size ~ 4
    42. 42. Rats  Nocturnal  Requires water daily  Will travel several hundred feet from nest  Prefer to travel on edges  Wary of new objects in the environment  They can jump, swim and squeeze into and through almost anything  Will eat pipes, wire, blocks, and whatever necessary to get to food Mice  Nocturnal  Generally get water from food source  Will travel long distances from nest  Prefer to travel on edges  Not wary of new objects in the environment  They can jump, swim and squeeze into and through almost anything  Live outside, in homes a sheds
    43. 43. Moles Important Facts: •live in underground runways •Seldom seen above the ground •Runways 5 to 20” deep •Prefer loose, moist soil •4 to 8” long - Blind •Carnivores – earthworms, grubs, beetles, insect larvae •Can eat 40lbs of food a day •Single litter – 3 to 5 •Life span – 3 years
    44. 44. Quail & Birds Important Facts: •Generally prefer open space during breeding •Omnivorous, but tent to be vegetarians looking for seed and seedlings •1 clutch per year – clutch size ~12 eggs •When quail reach 2 months old they can breed •Life span 3 – 5 years
    45. 45. Resources    Nevada Department of Wildlife   775-688-1500 Reno office  For general questions or comments  Nevada Department of Agriculture   405 South 21st Street, Sparks, NV 89431  775-353-3638
    46. 46. Companion PlantingPlanting a variety of flowers will attract many of the beneficial insects. •Flowers in the sunflower (Asteraceae) family consist of many small flowers which attract many beneficial insects. •Carrot family (Apiacea) •Buckwheat family (Polygonaceae) •Scabiosa family (Dipsaceae)
    47. 47. Simple rules for crop rotation: • Don’t follow tomato, peppers or eggplant with potatoes, or each other. • Allow 3 years before replanting the same group in any given bed. • Onions may be planted throughout all groups. • Beets, carrots and radishes may be planted among any group, and replanted as early crops are removed. • Interplant with companion plants to minimize pesticide use. • Keep good records so you can duplicate successes. PennState – Crop Rotation
    48. 48. Incorporating age old techniques Biochemical Pest Suppression Some plants exude chemicals from roots or aerial parts that suppress or repel pests and protect neighbouring plants. Insect Plants that should deter Aphid Chives, Coriander, Nasturtium Ants Tansy Asparagus Beetle Pot Marigold Bean Beetle Marigold, Nasturtium, Rosemary Cabbage Moth Hyssop, Mint (also clothes moths), Oregano, Rosemary, Sage, Southernwood, Tansy, Thyme
    49. 49. Insect Plants that should deter Potato Bugs Horseradish Mosquitoes Basil, Rosemary Moths Santolina Squash Bugs & Beetles Nasturtium, Tansy Tomato Horn Worm Borage, Pot Marigold Carrot Fly Rosemary, Sage Flea Beetle - Catmint, Mint Flies - Basil, Rue Japanese beetles - Garlic & Rue (When used near roses and raspberries), Tansy
    50. 50. Season extender-shade-rodent and insect exclusion  Row Cover  Burlap  Wall-of-waters  Sheets, or blankets  Don’t forget to save old tomato cages  Commercial cold frames  Or homemade cold frames of Plexiglas, old windows, or sheet plastic
    51. 51. Protection cont. Floating Row Covers  Frost protection  Warmer microclimate  Wind protection  Excludes insect pests  Reduced evapotranspiration  Good for beans, beets, carrot, cole crops, corn, lettuce, parsley, potato, radish, scallions, and spinach
    52. 52. Thank you & Happy Gardening Wendy Hanson Mazet Reno office – 775-336-0246 Douglas County – 775-782-9960