Tom Kuhar Professor of Entomology Virginia Tech Insects/arthropods in Agriculture
What immediately comes to mind?
Pests - Anything that interferes with the human objective.
- Generally, herbivores Insects are part of any Agroecosystem Ecological Importance of Insects
Insects comprise 97% of all animals They are essential to most Food Webs: - main consumers of plants, - major role in consuming other insects - recycle large plant & animal matter into smaller organic matter. Soil aeration Pollination The vast majority of insects are beneficial! Hymenoptera
• The 3 P’s Pollinators Hymenopteran predators Hymenopteran Parasitoids
Ichneumonids and Braconids Trichogrammatids Bracon spp. attack noctuid larvae ~25% of Diamondback moth larvae Tachinids of larvae
can parasitize up to 90% of aphid population
• introduced for ECB • May parasitize ~25% of larvae Hymenoptera: Braconidae/Ichneumonidae Primary Prey: larvae and pupae of most insects Key Characters: aphid “mummies”, cocoons Vegetable crops: most can parasitize up to 80% of Diamondback moth larvae Lepidoptera (Moths & Butterflies)
Complete metamorphosis Larvae (caterpillars) Chewing leaves and boring into fruits
Corn earworm Imported Cabbageworm Lepidoptera: Pieridae (Butterfly)
Overwinters as a chrysalis multiple generations/yr Adults are white butterflies Eggs deposited on leaves Armyworms (Spodoptera spp.)
Fall Armyworm
Beet Armyworm Armyworms (Spodoptera spp.)
Southern Armyworm
Yellowstriped Armyworm Hornworm Lepidoptera: Sphingidae Some lepidopteran larvae bore into plants European corn borer
Snap bean
Adults Potato
Egg mass
Corn Bell pepper Squash vine borer Lepidoptera: Sesiidae
Beetles (Coleoptera)
Complete metamorphosis Most abundant and diverse insects Chewing mouthparts Colorado potato beetle CUCUMBER BEETLES Striped cucumber beetle
Spotted cucumber beetle Cucumber beetle aggregation Asaparagus beetles (Chrysomelidae) Flea beetles (many species) Beetles are also important predators of insects Ladybeetles (not ladybugs) Mexican bean beetle Subterranean: Wireworms & white grubs Other subterranean insects that damage seeds and roots Seedcorn maggot Delia platura (Anthomyiidae) • Below-ground insect that attacks the germinating seed • Typically a problem when germination is delayed in cool wet soils • Prefers high organic matter soils (manure applied) Cabbage maggot Delia radicum (Anthomyiidae) Onion maggot Delia antiqua (Anthomyiidae) Sucking insect pests of vegetables
Aphids • Multiple species can attack vegetables • Most species feed on multiple host plants • Sap sucking feeders • Possess cornicles “tail pipes” • Winged adults • Asexual reproduction (parthenogenesis) • Produce honeydew Prefer undersides of leaves Green peach aphid Myzus persicae
Alate (winged) adult Apterous (wingless) colony
Prefer: spinach, peppers, brassicas Melon aphid
• Aphis gossypii (AKA cotton aphid)
Prefer: squash, pumpkin, okra Corn Leaf Aphid Rhopalosiphum maidis (Fitch)
• Sucks sap from plants and deposits "honeydew," which can become moldy, giving the tops of the plants a black, sooty appearance • Attacks corn and small grains Potato aphid • Macrosiphum euphorbiae • Prefers tomato, and fall potato Cabbage Aphid Brevicoryne brassicae
Prefer: brassicas How can aphids hurt your crop?
• Can attain very high densities on young plant tissue, causing water stress, wilting, and reduced plant growth. How can aphids hurt your crop?
• Contamination of harvestable plant material with aphids • Contamination of vegetables by aphids sometimes presents quarantine problems How can aphids hurt your crop?
• Produce sticky honey dew and sooty mold growth How can aphids hurt your crop?
• Aphids are the major vectors of plant viruses • Both persistent viruses, which move through the feeding secretions of the aphid, and non-persistent viruses, which are only temporary contaminants of aphid mouthparts, are effectively transmitted. • > 100 viruses transmitted by aphids. Some of the particularly damaging diseases include potato leafroll virus and potato virus Y to Solanaceae, beet western yellows and beet yellows viruses to Chenopodiaceae, lettuce mosaic virus to Compositae, cauliflower mosaic and turnip mosaic viruses to Cruciferae, and cucumber mosaic and watermelon mosaic viruses to Cucurbitaceae.
PVY CMV
Important natural enemies Insecticidal soap
• Potassium salts of fatty acids Chemical control: Thorough spray coverage beneath leaves is important when foliar sprays are used Potato Leafhopper Empoasca fabae Hemiptera: Cicadellidae Potato Leafhopper Hopperburn • Serious pest of potato, beans, eggplant • Effectively controlled by neonicotinoids and many other insecticides Stink bugs Hemiptera: Pentatomidae)
Brown stink bug Dusky stink bug
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Harlequin bug Murgantia histrionica • Brassica specialist (southern pest) • Overwinters as adult in brassica fields Brown marmorated stink bug • Halyomorpha halys (Stål) • Probably introduced to the U.S. in the 1990’s from China on shipping cargo Orchard CropsVery wide host range Brown Marmorated Stink bug Life cycle of BMSB Many bugs are important predators of pest insects
Major thrips species in Virginia
• Eastern flower thrips, Frankliniella tritici - accounts for 90% of species in tomato - found in blossoms, injures fruit - does not vector TSWV
• Tobacco thrips, F. fusca - primarily a leaf feeder - vectors TSWV
Thrips larva Western flower thrips, F. occidentalis • Major greenhouse pest • Sporadic pest in the field • Very difficult to control – insecticide resistance Thrips injury
Dimpling
Gold flecking Tomato Spotted Wilt Virus
TSWV
T S Numerous other types of insects Pest Management
Humans taking action to prevent pests from causing economic loss Pest Management Approaches
Conventional Organic
High agrichemical inputs No synthetic chemicals Maximize yield per acre Systems approach Reduce impact on environment Insecticides to control vegetable pests
Pyrethroids • Lambda-cyhalothrin (Warrior II, others) • Bifenthrin (Capture, Brigade, Sniper, Bifenture, other generics) • Esfenvalerate (Asana XL) • Permethrin (Ambush, Perm-up, etc..) • Beta-cyfluthrin (Baythroid XL) • Cyfluthrin (Tombstone) • Fenpropathrin (Danitol) • Zeta cypermethrin (MustangMax) • Zeta cyper. + bifenthrin (Hero EC) Many pyrethroid resistant pests in vegetable systems Organic PEST MANAGEMENT
Large-scale commercial organic agriculture still uses pesticides - Some are neurotoxins or other substances that may be broad spectrum (kill or harm beneficials arthropods) • Integrated - Select from list of appropriate tools: – Biological – Host plant resistance – Physical – Cultural – Regulatory – Chemical
• Goal is management of insect pest problems Is there really a pest problem?
Bean leaf beetle (Chrysomelidae) CUCURBIT PLANTS CAN OFTEN OUTGROW DEFOLIATION
It is primarily young cucurbit plants that are vulnerable. In fact, older plants can tolerate as much as 25% defoliation due to beetle feeding with no reduction in yield (Hoffmann et al., 2002, 2003). Threshold = 1 beetle/plant on small plants 5 beetles per plant on large plants INTEGRATED PEST MANAGEMENT (IPM)
Using multiple strategies for pest control
Emphasizing the safest and most sensible and effective treatments
Using ACTION pest thresholds to determine exactly when/if treatment is necessary “IPM” Integrated Pest Management
(First Line of Defense) Selecting proper seed and varieties
Disease tolerance Seed treatments Tomato Seeds - Mountain Glory VFFF/TSWV - Hybrid Bush Tomato Variety - 25 Seeds Bt transgenic sweet corn
• Several hybrids commercially available (Syngenta Seeds, Monsanto among other companies) • Very effective – provide 80-90% control ear & stalk protection Bt sweet corn evaluations in VA (Kuhar, Taylor, Doughty, and Blevins)
% marketable ears 100.0 80.0 60.0 40.0 20.0 0.0 Suffolk Painter Abingdon Whitethorne non-Bt Cry1Ab Cry1Ab + Vip3A
Providence BC0805 Remedy Cultural or environmental control tactics
Manipulation of environmental conditions to limit insect populations Cultural Control – crop rotation, planting dates Avoidance Trap cropping Cultivation Crop rotation: Colorado potato beetle Row covers & Reflective mulch for pest control
Can reduce thrips and aphid numbers landing on plants Trap cropping Growing a more attractive crop in proximity to a cash crop will Divert herbivore feeding from cash crop
Concentrates herbivores concentrate chemical management Trap crop mustard rows protect collards from harlequin bugs Augmentative Biological Control • Relatively few successes in the field for vegetable pest management (we’ll discuss a couple) • Greater success in greenhouse IPM systems Predatory mites Encarsia for whiteflies What are these? Braconid: Aphidiinae – aphid parasitoids • Wasp parasitoids of Aphids
can parasitize up to 90% of aphid population Banker Plants
• Provide a source population of aphid parasitoids Banker plants for aphid control in greenhouses • Parasitized bird cherry-oat aphids on barley • Aphidius colemani, rate of 500 wasps on eight barley plants • Parasitoids also attack green peach aphid and melon aphid Trichogramma parasitoids
Easy to rear (sterilized grain moth eggs) Minute in size (very little space) Complete generation in about 2 weeks Biological Control - parasitoids
Diadegma insulare Farmscapes PEST MANAGEMENT
FOOD WEBS ARE COMPLEX! - Calling in more pests? - Providing a pest refuge? - Distracting predators?
PEST MANAGEMENT
FOOD WEBS ARE COMPLEX!
Intra-guild predation
Conservation Biological Control Avoid spraying insecticides that kill natural enemies Insecticides to control vegetable pests
Pyrethroids • Lambda-cyhalothrin (Warrior II, others) • Bifenthrin (Capture, Brigade, Sniper, Bifenture, other generics) • Esfenvalerate (Asana XL) • Permethrin (Ambush, Perm-up, etc..) • Beta-cyfluthrin (Baythroid XL) • Cyfluthrin (Tombstone) • Fenpropathrin (Danitol) • Zeta cypermethrin (MustangMax) • Zeta cyper. + bifenthrin (Hero EC) Melon aphid densities after insecticide sprays on pumpkin for squash bug – Painter, VA
Treatment Rate Aphids/2 leaves mid-July (acre)
Asana XL (esfenvalerate) 9.6 fl oz 200.0 a Danitol 2.4EC (fenpropathrin) 10.66 fl 223.0 a oz Danitol 2.4EC 16 fl oz 500.8 a UTC 102.0 b 2011– Stink bug insecticide test: Bell Peppers , Blacksburg, VA (4 weekly sprays @ labeled rates)
% stink bug fruit damage % control Mean no. green Treatment (stink bug dmg peach aphids / 8-Aug 19-Aug 30-Aug reduction) 20 leaves Untr. Control 40.0 15.0 32.5 - 2.8 Zeta cypermethrin 7.5 8.8 7.5 72.8 155.0 Zeta cypermethrin + bifenthrin 17.5 2.5 10.0 65.7 1014.0 Beta cyfluthrin 25.0 6.3 10.0 52.8 201.8 Scouting and Sampling for Pests Before Spraying Action or Economic Pest Thresholds
Uses pest threshold densities to determine when a treatment should be applied
Economic Injury Level *point of economic loss*
Economic Threshold Pest Population Pest *time to treat*
Time Most of the new insecticides Narrow spectrum (targeted) Reduced mammalian toxicity Reduced impact on beneficial organisms Reduced impact on the environment Sometimes a preventive systemic insecticide is a good choice Neonicotinoid insecticides
• Imidacloprid – Admire, Merit, Gaucho ST, Provado, Advantage, many others • Thiamethoxam – Platinum, Meridian, Cruiser ST • Dinotefuran – Safari, Zylam, Venom, Scorpion • Clothianidin – Poncho ST, Belay, Arena • Acetamiprid - Assail
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Neonicotinoid facts
• Similar mode of action as nicotine, but far less toxic to mammals • Relatively low toxicity to mammals • Selective insecticides that usually are more IPM-friendly than what was sprayed before or what would be sprayed instead • Not all neonicotinoids are created equal – Assail (acetamiprid) is 100x less toxic to bees than other neonic compounds • When used correctly, they often are less ecologically impactful than other tactics At-planting/Seed-piece insecticide trial on potatoes – Painter, VA
Mean no. CPB/10 stems Mean no. CPB/10 - 25 May stems - 30 May Rate Prod. (76 DAP) (81 DAP) Leafhoppe per cwt seed rs/10 Treatment or per Ac. for Small Large Small Large leaves in-furrow larvae larvae larvae larvae (88 DAP)
Untreated Control 66.8a 36.3a 44.5a 47.0a 25.5a
Platinum 0.17 oz/cwt 0.0b 0.0b 9.8b 0.0b 0.8c (Thiamethoxam) Thiamethoxam 5 oz/A 0.0b 0.0b 2.3b 0.0b 2.3bc
Admire Pro 0.17 oz/cwt 0.0b 0.3b 16.3b 3.8b 5.8b (Imidacloprid) Venom (Dinotefuran) 7.5 oz/A 0.0b 0.0b 6.0b 0.0b 0.0c SEED TREATMENT
Contains the neonicotinoid systemic insecticide – Thiamethoxam Also contains fungicide active ingredients in Apron XL®, Maxim® 4FS and Dynasty® Purchase seed from dealer pre-treated with FarMore
For a standard pumpkin variety: 1000 seeds untreated = $100 1000 seeds with Farmore = $110 WHAT HAPPEN TO THIS SEED? SEED TREATMENT WILL ALSO CONTROL SEEDCORN MAGGOT
Below-ground insect that attacks germinating seeds Typically a problem when germination is delayed in cool wet soils Prefers high organic matter soils (manure applied) BEETLES EMERGE FROM OVERWINTERING AND MASS ON CUCURBIT PLANTS IN SPRING Dively GP, Embrey MS, Kamel A, Hawthorne DJ, Pettis JS (2015) Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health. PLOSOne. http://dx.doi.org/10.1371/journal.pone.0118748
“The most likely encountered high range of field doses relevant for seed-treated crops (5 μg/kg) had negligible effects on colony health” 115 Efficacy of Verimark applied to potato seed
Dead CPB @ 70 DAP Seed-piece treatment
Slug Control Products Metaldehyde Baits Typically applied as slug pellets, which normally include a wheat bait. Metaldehyde acts on the pest by contact or ingestion, and the aqueous environment inside the pest's cells readily hydrolyzes metaldehyde into acetaldehyde, the molecule associated with an alcohol hangover. • Deadline M-Ps (Amvac) - 10-40 lbs/A • Metarex (Liphatech) –(extruded – steam process) -- 5-40 lbs/A • Axcela (Lonza) - new extrusion technique, gelatinized pellet Other Slug Control Products
• Sluggo (Certis) – iron phosphate -federal and state label in DE - 20-44 lbs/A (OMRI Certified)
• IronFist (Engage Agro/Neudorff) 2% Sodium Ferric EDTA (Ethylenediaminetetraacetic acid – binds to metals) - wheat-based bait (2%) -- 10-40 lbs/A • Ferroxx (Neudorff) – 5% Sodium Ferric EDTA - 5-20 lbs/A
• Lannate LV – (methomyl) - carbamate The end.
QUESTIONS?