Greenhouse Insect Biology and Management

Greenhouse Insect Biology and Management Jen White & RicBessin Dept. Entomology University of Kentucky

Pest management in greenhouses

Why are pests attracted to greenhouses? Lots of food Great climate No enemies

Outline • Introduction to Integrated Pest Management • Biology of common greenhouse pests • Chemical controls Next time: • Biological and Alternative controls

Integrated Pest Management Goal: Mitigate pest damage while protecting human health, the environment and economic viability • Integration of tactics • Biological • Chemical • Cultural • Physical/mechanical • More reliable control

Components of an IPM Program • Pest prevention • Pest identification • Monitoring and population assessment • Control action guidelines • Integration of tactics • Biological • Chemical • Cultural • Physical/mechanical

Prevention Keep them out! • Inspect incoming stock • Isolation • Mechanical exclusion • Weed removal • Inside and outside GH • No extra flowering ornamentals • Prevent year-to-year carryover • Remove residues • Sanitize

Pest Identification • Why is it important? • Misidentification can contribute to failure • Incorrect biological or chemical controls

Common Greenhouse Pests • Mites • Thrips • Whiteflies • Aphids • Fungus gnats • Shore flies • Mealybugs • Others… Characteristics • Small • Hidden • Short life cycle • Numbers build fast

Relative Sizes Aphid Thrips Mealybug Mite Whitefly Shore fly Fungus gnat

Common Greenhouse Pests • Mites • Thrips • Aphids • Whiteflies • Mealybugs • Fungus gnats • Shore flies • Others…

Mite identification • Tiny • Webbing

Mite identification • Tiny • Webbing • Eight legs, no wings • NOT insects • Two spots – • Two spotted spider mite • Other species • Lewis, Broad, Cyclamen

Spider Mites • Attack 300 + species of plants • Life cycle in 8+ days • Females lay 100+ eggs • Sap feeders • Under leaves, around buds • Prefer tender leaves • Two-spotted • spider mite

Mites: Monitoring • Scouting • look for stippling, mottled leaves • webbing • premature leaf drop • Examine under leaves

Mites: Management • Cultural • Reduce plant stress • Spritz with water

Thrips Identification • Tiny • Yellow-ish • Linear • Most common: • Western flower thrips

Thrips Damage • Deformed leaves • Decaying flowers • Silvery, flecked scars • Black fecal spots

Thrips Biology • Pierce plant cells • Young growth and flowers • Tightly furled • Mainly females • 150 to 300 eggs • Life cycle: 12+ days • Vector tospoviruses • Impatiens necrotic spot virus (INSV) • Tomato spotted wilt virus (TSWV) Western flower thrips

In soil In plant

Thrips: Monitoring • Early detection • Blue or yellow cards • Minimum of 3 • Placed near doors/vents thrips sensitive plants • 1 per 2000 ft2 minimum • Placed just above canopy • Can do a subset of grids • New cards periodically • Tap method • Same person, regular basis (weekly)

Thrips: Management • Cultural Control • Remove weeds (that may harbor viruses) • Crop alternation • Petunia as virus indicator plant • Sensitive to virus • Not systemic • Use vegetative plants • Blue plastic plate to attract Western flower thrips “Cascade blue” “Summer madness”

Common Greenhouse Pests • Mites • Thrips • Aphids • Whiteflies • Mealybugs • Fungus gnats • Shore flies • Others… Melon or cotton aphid

Aphid identification Melon or cotton aphid • Pear shaped body • Cornicles = “tailpipes” • Most common species >135 plant families Green peach aphid Potato aphid >125 plant families >90 plant families Whitney Cranshaw Joseph Berger

Aphid Biology • High reproductive rate • 100 live young/female • Asexual • Live birth • Life cycle 7-10 days • Remove sap • Produce honeydew

Aphid Damage • Stunt plants • Curling, cupping of leaves • Sticky honeydew • Sooty mold • Transmit viruses

Aphids: Monitoring Yellow cards: caution! Scouting • Insects on stems, fresh growth, under leaves • Sticky honeydew on leaf surface Most aphids don’t have wings!

Aphid Management • Avoid excess Nitrogen Whitney Cranshaw

Whitefly Identification Greenhouse Trialeurodesvaporariorum Sweet potato or Silver leaf Bemisiatabaci Photo credit: Gaucho Banded winged Trialeurodesabutiloneus Ronald Smith UGA857007

Whitefly Identification Greenhouse Trialeurodesvaporariorum Sweet potato or Silver leaf Bemisiatabaci

Whitefly Biology • All stages under leaf • Sedentary immatures • Life cycle in 1 month • Highly visible • MANY host plants Greenhouse whitefly

Whitefly Damage • Yellowing and discoloration • Stunt plants • Honeydew and mold • Virus transmission

yellow cards plant inspection Undersides of leaves Honeydew Sooty mold Shake plant for adults Whiteflies: Monitoring Sweet Potato Whitefly

Cultural control Plant-free periods Time depends on temperature ->cooler temps, keep plant-free longer Whiteflies: Management

Mealybugs • “Big”: ¼ inch • Waxy, cottony, fringed • Sucking insects • produce honeydew • stunt plants • Attack all parts of plant • Life cycle: 1 month • Reduce marketability

Mealybugs: Monitoring • Scouting • White flecks on midribs, leaf axils, leaf underside • Honeydew and sooty mold

Fungus Gnats • Small, delicate flies • Feed on root, stems, decaying debris • Need damp media • Life cycle 1 month • May promote diseases • Pythium, Verticillium, Botrytis • Watch pet (wet) plants !

Fungus Gnats: Monitoring • Yellow cards • Horizontal orientation • Potato disks http://www.omafra.gov.on.ca/english/crops/facts/06-079.htm

Fungus Gnats: Management • Cultural control • Less water! • Remove standing water • Sterilize/contain compost

Shore Flies • Small, robust flies • Feed on algae • Must have damp media • Leave frass on plants • May move Pythium spores

Shore Flies: Management • Cultural Control • Eliminate algae

Build an IPM Monitoring Program • Start simple • Careful inspection • Scout at least once per week • Designate pest management units (PMU) • Have some prior knowledge of problems • Keep good written records (database)

Greenhouse Insect Biology and Management