grow your own, nevada! fall 2011: controlling pests

Controlling Pests in Your GardenHeidi Kratsch

University of Nevada Cooperative Extension

Pests common in northern Nevada

• Insects (many different kinds!)

• Weeds

• Rodents (and other unwanted varmints)

• Diseases (rare, mostly caused by cultural problems)

1. Determine the cause of the problem.

2. Set a tolerance level beyond which control is justified.

3. Use the least toxic methods first.

4. Apply a pesticide as a last resort.

Integrated Pest Management (IPM)

The key to an effective integrated pest management program is regular monitoring to detect the pest when it first becomes

active.

• Physical and cultural▫ Hand-collecting, proper watering, good sanitation

• Biological▫ Use of resistant plant varieties

▫ Natural predators (beneficial insects)

▫ Naturally occurring chemicals

• Chemical▫ Herbicides, insecticides, fungicides

Types of Control

Insect Lifecycle• Time controls to target insects

when most vulnerable.

• For many, this is at first hatch or in the adult before eggs are laid.

• Especially important for insects that get into the flowers or fruits.

• Weed control

• Watering

▫ Spraying foliage with water occasionally

▫ Spider mites are attracted to dusty, dry foliage.

• Fertilizing

▫ Overfertilizing makes leaves more attractive to aphids.

• Crop rotation

▫ Don’t allow pests to build-up in the soil.

▫ Many pests prefer specific families.

Cultural Controls

Spider mites on the underside of a leaf

• Hand-picking larger pests

▫ Squash bugs and eggs, slugs, snails, caterpillars

• Barriers and traps

▫ Fences

▫ Pheromone traps (for monitoring)

▫ Sticky cards and tree bands

• Remove infested plants

Physical Controls

Natural Predators

• Assassin bugs

• Parasitic wasps

• Lady beetles

• Lacewings

• Snake flies

• Praying mantis

• Syrphid flies

• Spiders

Examples

Tomato hornworm parasitized by a Braconid wasp - the white cocoons house the larvae that will emerge as adult wasps.

Lady beetle larva attacking and eating aphids on a leaf

• Microbial sprays –▫ Bacillus thuringiensis (Bt)

▫ Talaromyces flavus

• Insecticidal soaps –dissolve waxy coatings on insect bodies

• Horticultural oils – work by smothering insects

• Botanicals –rotenone, neemoil, pyrethrum

Biological Pesticides

Pyrethrum is derived from certain species of chrysanthemum. It should not be confused with the more toxic pyrethroids.

How does Bt work?

1. Caterpillar eats leaves treated with Bt.

2. Toxins bind to receptors in the gut of the insect.

3. Gut wall breaks down allowing bacteria to enter

4. Caterpillar dies of severe bacterial infection within 2 days.

- Safe for organic production.

- Each strain is specific for a particular pest.

Cabbage family

Carrot family

Cucurbits

Corn (and other

grains)Lily family

Nightshade family

Legume family

Crop Rotation Scheme

Vegetable plant families

• Cabbage family: ▫ broccoli, brussels sprouts, cabbage, kale, radish

• Carrot family▫ Carrots, cilantro, dill, fennel, parsley

• Cucurbits▫ Cucumber, melon, pumpkin, squash

• Grass family▫ Corn and other grains (many cover crops)

• Lily family▫ Garlic, leeks, onions, shallots

• Nightshade family▫ Tomato, potato, eggplant, peppers

• Legume family▫ Beans, peas

Floating row covers

• Block insects

• Protect plants from cold/frost

Earwigs

Trapping is very effective against earwigs.• Trap in tuna cans baited with

fish oil or bacon grease.

• Attracted to decaying animal matter.

• Place traps near the problem areas and check them each morning. Shake live insects into a pail of soapy water to kill them.

Aphids

• Pear-shaped, winged or wingless – many colors

• Common on young shoots of many crops

• Produce 10+ generations/year asexually – live females

• Use floating row covers

• Hose off with a strong stream of water.

• Many natural enemies

• Avoid high N fertilizers

• Control ant populations Aphids suck the juices out of tender young tissues.

Lady beetle lunching on aphids

Flea beetles

• Adults chew holes in the leaves of seedlings; young live underground.

• Favor corn and crops in the nightshade family.

• Control weeds and remove garden debris.

• Use floating row covers.

• Remove and discard dead or badly damaged plants.

• Spray with neem oil.

Beet Armyworm• Attracted to

lettuce, cabbage, beans, peppers, tomatoes, spinach, onion, beets

• Eat all parts of the plant –skeletonize leaves.

• Do not overwinter here – blow in from Arizona.

• Hand picking – monitor in August and September.

• Many natural enemies.

Corn Earworm

• Adults lay eggs on the foliage.

• Larvae feed within the ears and on silks and tassels.

• Deep cultivation of soil in spring exposes/kills pupae.

• Plant as early as possible.

• Place a rubber band around the cob top when silks first appear.

• Use horticultural oils

• Bt for corn earworm

Cutworms

• Adults are moths; the worms (larvae) curl into a “C” when disturbed.

• Eggs are laid on leaves and stems near the ground.

• The larvae clip stems just below the soil surface; may chew holes in leaves.

• Most active at night; scout and hand pick.

• Protect seedlings with cardboard collars.

• Apply 5% carbaryl bait to the soil for heavy infestations.

Spider mites

• Found on undersides of leaves; webbing sometime present.

• Manage dust build-up on leaves.

• Life cycle of only 7 days!

• Spray with insecticidal soap, horticultural oil, or neemoil.

• Malathion for severe cases

• Overuse of pesticides destroy spider mite predators.

• Attack: melon, raspberry, eggplant, beans, etc.

Source: Utah State University Cooperative Extension

Spider mite stippling on eggplant leaves

Squash bugs Vs. Stink bugs

Squash bugs are specific to cucurbits

• Good garden sanitation (remove debris).

• Hand pick adults and eggs.

• Trap adults with board or burlap set in the garden at night.

• Use floating row covers.

• Spray undersides of leaves with insecticidal soap.

• Apply neem oil to base of plant.

• Insecticides provide only temporary control.

Like stink bugs, squash bugs give off an unpleasant odor when crushed.

Stink bugs

Stink bug damage on tomato fruit

• Control weeds, esp. Russian thistle, common mallow, mustards.

• Adults overwinter on the ground under leaves – remove debris at the end of the growing season.

• Insecticidal soaps are effective.

Note the shield shape of the body.

Insect Control Summary

• Use physical or cultural methods first.

▫ Monitor your garden early and regularly.

▫ Encourage natural enemies.

▫ Avoid monocultures (confuse the pests!).

▫ Good sanitation.

• Use biological controls if physical controls don’t work (may need multiple applications).

• Use pesticides as a last resort.

Weed control

(don’t let this

happen to you!)

• Weeds rob your crops of water, nutrients and sunlight.

• Identify what it is and control it early.

• Compost annual weeds that haven’t gone to seed.

• Destroy perennials weeds, esp. the roots.

Preparing your beds

• Rotary tilling: only works for annuals, and temporarily.

• Pre-sprouting: Amend and water your bed – hoe the weeds that sprout before planting crops.

• Soil solarization: works for third season gardens

▫ Need temps above 80 F for 4 to 8 weeks.

▫ Use clear UV-resistant plastic

▫ Must be in contact with soil for best effect.

▫ Seal edges with bricks or dirt.

Water your beds before covering with plastic.

Herbicidal Soaps

• Weed-Aside™

• Contact herbicide, does not kill the roots.

• Work best on annuals and newly sprouted perennials.

• Safe around fruit and vegetable crops

• Use when weather is warm and dry.

• Best results with young actively growing weeds less than 5" high.

Winter Annual Weeds

• Germinate in fall/winter.

• Flower and set seed in spring.

• May reseed themselves before

fall crops are planted.

Flixweed

Redstem filaree

Prickly lettuceCommon mallow

Summer Annual Weeds

Lambsquarters

Crabgrass Redroot pigweed Russian thistle

Common purslane Spotted spurge

Perennial Weeds

Some have food storage organs that sprout new shoots.

tuber

Johnsongrass Yellow nutsedge DandelionSedges

Chickweed (Stellaria media)

• Winter annual

• Prefers cool weather.

• Can even germinate under snow cover.

• Low growing with smooth pointed leaves

• Easy to pull when plants are young.

• Herbicidal soap is effective if temperatures are warm.

• Solarization effectively kills seeds before they germinate.

Prickly lettuce (Lactuca serriola)

• Winter annual

• May cross with garden Lactucas (lettuces) by insect pollination – seeds will grow a bitter lettuce.

• Plant parts ooze a milky sap when broken.

• Seeds are wind-dispersed; control before it goes to seed.

• Pulling when plants are young is the most effective control.

Flixweed (Descurainia sophia)

• Winter annual

• In the Cabbage family (with broccoli, radish, mustards); will not cross with these crops.

• Produces lots of seed, which can build up in the soil and survive for years.

• Prevent seed production.

• Pull when in the seedling stage.

• Pre-sprouting is a good strategy for reducing the seedbank.

Crabgrass (Digitaria spp.)

• Summer annual

• Thrives in hot, moist areas.

• Stems can root wherever they touch the soil; can spread rapidly.

• Frequent shallow watering favors their persistence.

• Pull when plant is small.

• Herbicidals soap is effective.

• Pre-emergent weed killer with trifluralin to prevent seed germination.

Lambsquarters

(Chenopodium album)• Summer annual

• Young tender leaves can be cooked like spinach or eaten raw.

• Very competitive; uses lots of water.

• Triangular leaves with wavy edges; powdery coating

• Seeds very long-lived.

• Remove seedlings when young – easy to pull.

• Herbicidal soaps are effective.

Purslane (Portulaca oleracea)

• Summer annual

• Fleshy, grows as a low spreading mat.

• Thrives in moist conditions but can survive dry periods.

• Each plant produces 240,000 seeds!

• Pull when seedlings are young AND remove from garden. Can re-sprout from stem pieces.

• Soil solarization to reduce seedbank.

• Pre-emergent herbicides with trifluralin.

Purslane is edible!

Spotted Spurge

(Euphorbia maculata)• Summer annual

• Aggressive, lots of seeds that germinate quickly

• Cut stems release a milky sap

• Pull out plants early in the season.

• Use mulch around desirable plants.

• Herbicidal soap is effective early.

Quackgrass (Elytrigia repens)

• Perennial grass weed that can reach 3 feet tall and produce rhizomes spreading 3-5 feet laterally.

• Before planting, thoroughly cultivate area and remove all visible rhizome pieces.

Yellow nutsedge

(Cyperus esculentus)• Perennial weed

• Resembles a grass but is actually a sedge (triangular solid stems)

• Tubers are edible – used by Paiute tribe – nutlike flavor.

• Spreads by tubers and by seed

• Remove plants

while they are

small.

Wildlife in your garden -mammals

• Legal status:

▫ Game species

▫ Furbearing

▫ Protected, sensitive or threatened

• Management guidelines:

▫ Hunting

▫ Trapping

▫ Baits /rodenticides

▫ Exclusion

Exclusion

• Eliminate access.

• Install barriers when animals are away.

• Use fine mesh wire to protect plants.

• Repair holes in fences.

Wildlife in your garden -birds

• Legal status:

▫ Game bird

▫ Protected by Migratory Bird Treaty Act

▫ Introduced feral species

• Management guidelines:

▫ Hunting

▫ Harassment restrictions

▫ Exclusion

▫ Chemical pesticides by licensed applicator only

Voles

• Unprotected species

• Feed on roots, stems, seeds, bulbs and tubers

• Active year round; found in dense cover

• Wooden mouse traps

• Zinc phosphide wheat (rodenticide) – use in noncropareas.

• Clear weeds and debris.

• Mesh cylinders for single plants

• Natural predators: owls, hawks, cats, dogs

Ground squirrels (and chipmunks)

• Unprotected species (except Palmers and Hidden Forest Uinta Chipmunks).

• Live in burrows.

• Devour whole vegetables in the seedling stage.

• Can gnaw on sprinkler heads and irrigation lines.

• Trap and euthenize; illegal to relocate because they may harbor plague.

• Bait traps with nuts, oats or melon rinds.

• Natural predators: hawks, eagles, rattlesnakes, coyotes

Cottontail Rabbits

• Game species – can’t shoot out of season

• Exclusion – must be dug deep!

• Live trap – may not relocate

• Blood meal works well.

• No toxicants

Quail

• Game bird – need a permit to hunt, capture or kill.

• Scare tactics – flashers

• Exclusion

Questions?

• Jon Carpenter, Environmental Scientist, NDOA (Wildlife Control)

• Jeff Knight, State Entomologist, NDOA (Insect Biology and Control)

• Sue Donaldson, Water Quality and Weed Specialist, donaldsons@unce.unr.edu

• Heidi Kratsch, Horticulture Specialist, kratschh@unce.unr.edu