Insect Control in the Organic Vegetable Garden

Outline

• Planning to avoid pests• Insect Monitoring and Identification• Fundamentals of Organic Insect Control

– Cultural Practices– Sanitation, exclusion– Attracting natural enemies– Botanical and biological pesticides

• Key vegetable insect pests and control strategies

Organic Control ‘Toolbox’Example for Cucumber Beetle

• Habitat for natural enemies• Grow cucurbit varieties less attractive

to beetles• Long distance crop rotation• Transplant vs direct seeding• Eliminate crop residues• Manipulate planting date (may miss

peak markets)• Row covers (may interfere with

weeding)• Mulch (may exacerbate other pests)• Trellis plants (labor)• Trap crops, baits and sticky traps

(labor, cost)• Approved materials

– Neem, Beauveria bassiana, kaolin clay, pyrethrin, spinosadSource: Univ. of Kentucky Entomology

First StepsManage Soil for Healthy Plants

• Soil test (pH, P, K, micronutrients)

• Organic matter (cover crops, compost)

• Fertility plan– Application based on

crop needs

• Avoid excess N• If planting in turf

– Till before planting– Check for grubs

Choose Less Susceptible Varieties

• Hairy-leaf varieties• Tight husked corn

– Corn earworm• Virus-resistance

– GMO– Tomatoes– Cucurbits

• Squash vine borer– ATTRA publication

Avoid Pest Insects in TimeGather info on key pests

• Early planted crops generally have lower insect pressure– Pests with multiple

generations– Stink bugs, whiteflies,

tomato fruitworm– Don’t prolong harvest

• Late planting– Pests that overwinter

locally– Cucumber beetles, bean

leaf beetles

Harvest before early July to avoid Pickleworm

Avoid Insect Pests in SpaceGarden Layout Plan (learn crop families)

• Rotate beds/plots to different plant families

• Avoid successive plantings of same crop in adjacent beds

• Maximize diversity– Interplanting– Mix different families– Add flowering plants

Keeping Records

Sampling Scheme

• Begin sampling at planting• Sample weekly by crop• Sample enough plants to

represent planting area, and that can be done in a reasonable time

• Records will document what’s present, and whether populations are increasing, or decreasing

Sampling Equipment

To Spray or Not to Spray

• Keep organic insecticides handy – Purchased, home-made

• Decision to spray based on– Experience– Insect’s potential for damage

• Type of damage (direct or indirect)

– Stage of plant growth– Population trends (sampling records)– Does insect have natural enemies; are they

present?

Evidence of Natural Enemies

Plants Can Tolerate Some DefoliationExample: Potatoes

Plant Growth Stage

Maximum DefoliationWithout Yield Loss

Plant emergence to early bloom

20%

Early bloom 30%

Late bloom till harvest

60%

Insect Identification

ID insects at least to Order, and if possible to Family

ClassificationKingdom -- Animal

     Phylum -- Arthropoda

          Class -- Hexapoda (= insects) 

               Order -- Lepidoptera (= butterflies and moths)

                    Family -- Noctuidae (= noctuids) 

                         Genus -- Helicoverpa

                              Species -- Helicoverpa armigera (Tomato fruitworm, corn earworm

Key Insect Orders

Orthoptera: Grasshoppers and Crickets

Hemiptera: True Bugs

Thysanoptera: Thrips

Key Insect Orders

Coleoptera: Beetles

Diptera: Flies

Key Insect Orders

Homptera: Aphids, whiteflies

Lepidoptera: Butterflies, moths

Hymenoptera: Ants, bees, wasps

Arachnids: Mites and Spiders

Spider mites

Spiders

Insect Metamorphosis

Incomplete (12%)• Grasshoppers• True bugs• Aphids, thrips

Complete (88%)• Beetles• Flies• Ants, wasps, bees

Tips to Identify Larvae

Lepidpotera (Caterpillars)

Coleoptera: Beetles

Tips to Identify Larvae

Hymenoptera: Wasps

Diptera: Flies

Quiz: What are these?

Hint: One on top will undergo complete metamorphosis; One on bottom; incomplete metamorphosis

Cultural PracticesTillage

• Disrupts insect pest

life cycles• Exposes them to

weather, predators• Destroys crop debris• Accelerates organic

matter decomposition• Depletes food for

microbes• Degrades soil structure,

erosion

MulchesOrganic

• Straw mulch– Retains soil moisture,

lowers soil temperature

– Habitat for predators (and some pests)

– Excellent for potatoes, cucurbits

MulchesPlastic

• Black– Speeds early season

crop growth

• Reflective:– Repels thrips, aphids– Reduces spread of

viruses

Melon-Virus ExperimentsCover crop as camouflage

• Annual rye planted between rows in late fall

• Virus incidence lower in cover crop treatments

• Reflective mulch also reduced virus incidence

0

50

100

2003 2004

Cover

No Cover

% Plants Infected with WMV

Sanitation

• Start with pest free transplants

• Remove crop residue after harvest

• Remove diseased plants

• Remove weeds– Establish perennial

and flowering plants for natural enemy habitat

Exclusion

High Pressure Spray(Aphids, mites, whiteflies)

Water Wand: Cecil Stokes; E-mail (theroseman@gbronline.com)

Attracting Natural EnemiesMaking use of Nature’s Services

• Use of hedgerows in farming– Small trees, shrubs– Perennial grasses,

forbs– Flowering annuals

• Begin growing before crop

• Provide food and shelter for natural enemies

Attracting Natural EnemiesInsectary Plants in the Garden

• Establish insectary border(s)– Pick plants for

successive bloom spring-fall

– Fruit trees, flowering shrubs, perennial and annual flowers

– Include low growing plants (ground beetles)

Insectary Plants

• Apiaceae (small parasitic wasps)– Fennel, coriander, dill,

wild carrot • Compositacae/

Asteraceae, mint family (predatory wasps and flies)– Daisy, chamomile,

zinnia, echinacea, spearmint, catnip

• Thyme, rosemary, clover– Bees, wasps, ground

beetles

Some Organic Insecticides

• Entrust (Spinosad)– Microbial fermentation

product– Targets: caterpillars,

thrips, leafminers, some beetles

– Soft on natural enemies, but toxic to bees

– $550/lb• 1 gram/5 gal• 450 tanks = $1.20 each

Bacillus thuringiensis

– BT kurstaki and aizawai• Controls caterpillars

– BT israelensis• Mosquito larvae

– BT tenebrionis• Beetle larvae

– Insects must eat treated foliage• Good spray coverage

– Better against small larvae

Neem

• Azadirachtin: extract from neem tree

• Multiple modes of action, including repellency

• Broad spectrum– Best against larvae– Also good on

whiteflies,aphids

Pyrethrin or Pyrethrum

• Extract from flowers of pyrethrum daisy

• Broad spectrum• Breaks down quickly

Insecticidal Soap

• Potassium salts of fatty acids

• Acts by smothering and can break down insect cuticle

• Best against soft bodied insects (aphids, whiteflies, mites)

Kaolin Clay

• Applied as a slurry before pests arrive

• Physical barrier, deterrent, irritant

• Mix well, remove sprayer filter

• Must wash fruit

Pepper and Garlic Sprays

BT Garlic Pepper Karate Neem Control

Cucurbit Pests

Squash Bug Control

• Crop rotation and sanitation are very important. Rotate next years crop to different area.

• During the summer, adults tend to congregate under shelter at night. Place boards on the soil surface near the squash in the evening and the next morning collect and destroy the pest.

• Destroy egg masses on the underside of leaves.• A parasitic fly, Trichopoda pennipes, affects adult squash bugs and

several wasps parastize the eggs. Provide habitat for these in or near the field.

• If squash bugs are a problem on your farm, avoid heavy mulch or no-till in susceptible crops such as zucchini. Squash bugs like shelter, and appear more numerous in reduced tillage or mulched crop systems.

• Pyrethrin and Neem products

Cucurbit Pests

Squash Vine Borer Control

• Winter squash, pumpkins and zucchini are particularly susceptible. Butternut squash (C. moschata) is resistant.

• Soon after crop harvest, plow the vine debris deeply to bury over larvae.

• Rotate fields.• In small plantings, it may be possible to manually

remove the larvae. Find the sawdust-like frass on the affected plant stem, and then locate the larva by slicing lengthwise along the stem until you reach it. Destroy the larva, and then cover the slit stem area with soil.

• Keep floating row covers in place after transplanting or direct seeding until flowering.

Cucurbit Pests

Cucumber Beetle Control

• Crop rotation and sanitation are important. • Floating row covers are very effective for avoiding beetle damage.

Remember to temporarily remove the covers periodically to weed early, and leave off permanently when the flowers appear to allow pollination.

• Use of trap crops. Cultivars vary dramatically in their attractiveness to beetles. The inexpensive variety Dark Green Zucchini and Blue Hubbard squash are effective trap crops.

• Yellow sticky cups or tape can trap adults. They should be replaced regularly as they become saturated with beetles and field debris.

• Use transplants instead of direct seeding. They will be older when beetles arrive and therefore more tolerant, or you can plant later after peak beetle activity is over.

Solanaceous Crop Pests

CPB Control

• Crop rotation• Propane flamer; young potato plants if infested• Mulch crops with straw or hay before adults

arrive• Hand picking• Entrust, Neem

Solanaceous Crop Pests

Flea Beetle Control

• Row covers• Spinosad• Neem products• Capsaicin gives some control (45% in one study). The

product, Miller’s Hot Sauce™ is OMRI-approved and labeled for use on crop plants as a mammal repellant. If so used, it will also reduce flea beetle damage.

• Pyrethrum: Pyganic™ has shown variable results• Kaolin clay (Surround™).

Sweet Corn Pests

Corn Earworm Control

• Corn varieties with long, tight husks impede the entrance of the worm somewhat, but these provide only partial control. Varieties that have been reported to be less susceptible to damage include: Silver Queen, Stowell’s Evergreen, Viking RB, Supersweet JRB, Golden Bantam, Jubilee, Texas Honey June, and Bodacious.

• Since the pest is usually not a problem until mid to late summer, planting early to schedule harvest before expected arrival of CEW and using short season varieties will help avoid injury.

• BT and oil (Zea-Later); apply when silks reach full length• Spinosad

Questionszehnder@clemson.edu