Presentation on theme: "Insect Management for Organic Vegetable Production"— Presentation transcript:
1 Insect Management for Organic Vegetable Production Richard WeinzierlDepartment of Crop SciencesUniversity of Illinois
2 Insect Management for Organic Vegetable Production An overview of practicesOverall cultural practices ... rotations, altered planting dates, crop residue destruction, etc.Pest exclusion and repellencyRecognizing and manipulating natural enemies (predators, parasites, and pathogens)Organic insecticides: botanical and microbial insecticides, soaps, oils, and othersA few specifics on ... sweet corn and cabbage
3 Learn about the pests ...Learn the life histories of major insect pests, disease, and weedsLearn to identify key insects, diseases, and weedsUnderstand WHY control is needed (if it is)Develop appropriate expectationsThink critically ... do you really believe that a particular practice or product or organism can work as claimed? Is it harmless or appropriate just because it is organic?
4 For background on entomology and pest management in general … For information on pest biology, occurrence, and management for commercial growers …Illinois Fruit and Vegetable NewsFor background on entomology and pest management in general …The web site for “Introduction to Applied Entomology”Good references:Garden Insects of North AmericaWhitney Cranshaw, Colorado State University, 2004Princeton Univ. Press; ISBN (paper back)Vegetable Insect ManagementFoster and Flood, 2005Meister Media; ISBN
5 Information sources Midwest Vegetable Production Guide Home, Yard, and Garden Pest GuideOrder from: https://webstore.aces.uiuc.edu/shopsite/C1391.htmlHome, Yard, and Garden Newsletter
6 What about reduced tillage, weedy cultures, and interplantings? Stable habitats and crop residues favor survival of predaceous and parasitic insectsSome plants are slightly repellent to certain insects“Complex” crop landscapes slow the buildup of some specialist pestsCrop residues and weeds also favor the establishment and success of some pestsWeeds may serve as winter / alternate hosts of crop viruses (CMV, for example)On the scale that affects insect movement and host plant identification and selection, ALL gardeners are practicing interplantings.
7 Natural enemies Predators, parasites, and pathogens To enhance their success ...Recognize them; know what they doMinimize insecticide useUse selective insecticides in selective waysMaintain favorable habitatsProvide alternative foods (pollen, nectar, etc.)
9 Naturally occurring predators The unsung generalist insectivoresGround beetlesRove beetlesPredaceous bugsPraying mantidsbirds and bats
10 Predators available for purchase Green lacewingsConvergent lady beetleSpined soldier bugPraying mantidsPredaceous mites (for greenhouses)
11 Parasites “Alien” in real life Most are very host-specific Importation, establishment, and conservation generally are more appropriate than purchase and release(Augmentation is more valuable in greenhouses than in most garden and field situations)
12 Parasites to purchaseEncarsia formosa against greenhouse whitefly in greenhouse productionTrichogramma ostrinia against Lepidopteran pests of vegetables, including sweet cornTrichogramma spp. develop completely within the eggs of their host
14 Insecticides: Botanicals, microbials, and other alternatives Appropriate IF ...they are low in toxicity to nontarget organisms (“selective”)they do not persist in the environment (and are not moved to unwanted destinations)Selectivity and short persistence are weaknesses as well as strengths
15 Insecticide references An Introduction to Insecticides, by George Ware, at Insecticides, Chemistries, and Characteristics, by Jeffrey Bloomquist, at
16 Botanicals Pyrethrins Rotenone From pyrethrin daisies Axonic poisons Low in toxicity to mammalsVery rapid breakdown ... no residual actionUsed to kill fleas and lice on humans and pets; labeled for use on many fruits and vegetablesRotenoneFrom roots of Derris and other tropical legumesDisrupts cellular respirationModerate toxicity to mammals (~ Sevin); very toxic to fishModerate persistence (~ Sevin)Used against many pests, especially beetlesNo longer on the NOP list of approved materials
17 Botanicals Sabadilla Ryania Sabadilla & ryania are not available now From seeds of a tropical lily & European Veratrum spp.Axonic poisonVery low in toxicity to mammals, but a severe membrane irritantBreaks down very rapidlyEffective against squash bug, harlequin bug, and citrus thripsRyaniaFrom woody stems of S. American Ryania shrubsCalcium channel poisonLow mammalian toxicityMore persistent than rotenone but less potentUsed against caterpillars in fruits and vegetablesSabadilla & ryania are not available now
18 Botanicals Neem Citrus oil components From all parts of Azadirachta and Melia spp.Mode of action unknownLow toxicity to mammals; used medicinallyVery short persistenceLabeled on many crops and landscape plants, especially against soft-bodied insectsCitrus oil componentsLimonene and linaloolFrom citrus oilsVery short persistenceLow acute toxicity to mammals, but some evidence of chronic toxicityLess toxic than crude citrus extractsMostly in pet shampoos, etc.
19 Botanicals Nicotine Citronella Pennyroyal Garlic Rosemary oil From tobacco, other Nicotiana spp., othersAcetylcholine mimicVery toxic to humans, orally and dermallyVery short persistenceUsed in greenhouses against aphids, thrips, and mitesNot on the NOP list of approved substancesCitronellaPennyroyalGarlicRosemary oilHot pepper?
20 Oils Dormant oils for fruit and landscape trees Stylet oils reduce virus transmission, may suppress powdery mildewSummer oilsAgainst mites, aphids, other soft-bodied pestsCoverage is essential (upper and lower leaf surfaces); oils kill by suffocating pests that are sprayed directly
21 Insecticidal soaps Salts of fatty acids Kill insects by disrupting membranes (including tracheal linings)Work only against those insects that are wetted by the spray ... no residual actionEffective against aphids, whiteflies, mites, and other soft-bodied, not-too-mobile pestsBest-known brand names are Safer’s and M-PedeMake your own? Generally ... NO !!!
22 Absorbents & abrasives Clays, diatomaceous earth, silica aerogelsdisrupt the insect’s cuticle and kill by dehydrationKaolin ... “Surround”
23 Elemental and naturally occurring chemicals Sulfureffective miticide (may cause plant injury)CopperArsenic no longer used
24 Microbials Bacillus thuringiensis kurstaki and aizawai Toxic only to Lepidopteran larvae (caterpillars)Must be ingested to be effectiveDegraded by ultraviolet light ... short residual activity on treated foliageGood targets: Leps on cabbage, hornworms and fruitworm on tomatoes, European corn borer on sweet corn, etc.Not effective against: larvae that bore or tunnel into plants without much feeding on the surfaceDipel, Agree, XenTari, and many others
25 Microbials Bacillus thuringiensis tenebrionis effective against Colorado potato beetle larvaeBacillus thuringiensis israelensiseffective against larvae of black flies, fungus gnats, and some mosquitoesBacillus popilliae and Bacillus lentimorbuseffective against larvae of Japanese beetles (but not very effective against other white grubs)Trade Names include Doom, Japidemic, Milky-spore
26 Microbials Spinosads … Entrust ™ by Dow Derived from a soil actinomyceteEffective against a range of insects, including corn earworm, Colorado potato beetle, the “worms” on cabbage and related cole crops, apple maggot, and (less so) codling moth
27 Microbials Viruses Fungi Protozoans Nematodes ... might be used against soil insects where moisture can be maintained
28 Alternatives in Insect Management Biological and Biorational Approaches
29 A few specifics …Sweet cornCabbage and broccoli
30 Sweet corn Target pests Seedcorn maggot Cutworms Corn flea beetle Northern and western corn rootwormsCorn leaf aphidCorn rootworm beetles, Japanese beetleCorn earworm, European corn borer
31 Site selection Avoiding seedcorn maggot damage Crop rotation greatest in soils high in organic matter, recently manured (including green manures); also greatest in cool, wet soilsCrop rotationAny rotation except corn after corn used to avoid damage by corn rootworm larvae, BUT ...Wireworms and white grubs most numerous following sod
32 Site selection Avoiding cutworm damage Black cutworm moths prefer to lay eggs in plots with winter annual weeds present in March and AprilCrop rotation is not in itself a factor
33 Planting dates Earliest plantings ... are least susceptible to EAR damage by corn earworm and fall armywormare most susceptible to damage by seedcorn maggot (and cutworms)
34 Hybrid selection Plant Stewart’s wilt resistant hybrids No OMRI- or NOP-listed insecticides will control corn flea beetles well enough to reduce transmission adequately
35 Controlling insect infestations RotenoneSome effectiveness against flea beetles, Japanese beetle, and rootworm beetlesBacillus thuringiensisAs sprays or granules, effective against European corn borer on whorl-stage corn(Ryania) + rotenone + pyrethrinsSold to control ear-feeding Leps, but not very effective
36 Corn earworm and corn borer ear damage What about? ...Corn earworm and corn borer ear damageBTs and standard botanicals are generally NOT effective, especially against CEW (though transgenic BT sweet corns are less damaged by earworms and related pests)EntrustTrichogramma ostriniaeOils (garlic, SunSpray, etc.) on ear tips?Early plantings escape peak infestationsChopping ear tipsHybrid selection
37 Corn leaf aphidThreshold = >50 aphids on >50 percent of tassels before pollination is 50 percent completeFor organic growers ... M-Pede (soap) or neem may provide some control, but usually the best approach is to ignore infestations. Let the lady beetles and lacewings and parasites and diseases take their course.
38 Cabbage and broccoli Target pests Cabbage maggot Flea beetles Cabbage aphid, turnip aphid, green peach aphidVirus transmission is NOT an issue in the midwestern US“Leps” ... cabbage looper, imported cabbage worm, diamondback moth
39 Site selection and residue management Crop rotationMore important for disease than insect controlSome benefit against maggots and cabbage aphidResidue destructionRemoves host plant material for root maggots, diamondback moth, others
40 Planting dates and varieties Earliest plantings are more susceptible to cabbage maggot damage (more a northern than southern pest)Lepidopteran pests and aphids are more numerous in later plantingsKraut cabbage varieties with some resistance to thrips are available
41 Early-season practices Buy transplants free of aphids and diamondback moth larvaeFor flea beetle control ... rotenone or floating row coversRow covers also exclude egg-laying adults of cabbage maggot and Lepidopterans (caterpillars)
42 Cabbage aphid Row covers provide early protection M-Pede (insecticidal soap) or neemLittle or no data support use of garlic oilRogue out infested plants
43 “Leps” Larvae of moths and butterflies cabbage looperimported cabbage wormdiamondback mothPopulations increase through the summer
44 Thresholds: based on % plants infested with live larvae of any of the 3 species ... Seedbed: 10 %Broccoli and cauliflowerBefore flowering: 50 %Maturing heads: 10 %CabbageBefore cupping: 30%Cupping to early head: 20 %
45 For Lep control ... Row covers provide early protection Bacillus thuringiensis kurstaki / aizawai ... Dipel, Agree, XenTari, and othersMost effective against young larvaeLeast effective against cabbage looperDiamondback moth resistance to Bt evolved in Hawaii and Florida as a result of field use in crucifers
46 In all vegetable crops, what benefits do weedy cultures and interplantings offer? “Homes” and food sources for beneficial insects (predators and parasites)Nonfood “dilution” for specialist pestsSources for pest insectsSources of crop virusesSmall-flowered plants are best for natural enemies ... umbelifers and clovers