Master Gardener Volunteer Management System Instructions
Grow Your Own, Nevada! Fall 2011: Controlling Pests
1. Controlling Pests in Your Garden
Heidi Kratsch
University of Nevada Cooperative
Extension
2.
3. Pests common in northern Nevada
• Insects (many different kinds!)
• Weeds
• Rodents (and other unwanted varmints)
• Diseases (rare, mostly caused by cultural
problems)
4. Integrated Pest Management (IPM)
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.
The key to an effective integrated pest management program is
regular monitoring to detect the pest when it first becomes
active.
5. Types of Control
• 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
6. 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.
7. Cultural Controls
• 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 Spider mites on the underside of a
in the soil. leaf
▫ Many pests prefer specific
families.
8. Physical Controls
• 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
10. Examples
Tomato hornworm parasitized by a
Braconid wasp - the white cocoons
house the larvae that will emerge as
Lady beetle larva attacking and
adult wasps.
eating aphids on a leaf
11. Biological Pesticides
• Microbial sprays –
▫ Bacillus thuringiensis (Bt)
▫ Talaromyces flavus
• Insecticidal soaps –
dissolve waxy coatings on
insect bodies
• Horticultural oils – work
by smothering insects
Pyrethrum is derived from certain
• Botanicals – species of chrysanthemum. It
rotenone, neem should not be confused with the
oil, pyrethrum more toxic pyrethroids.
12. 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.
13. Cabbage
family
Legume Carrot
family family
Crop
Rotation
Nightshade
family
Scheme Cucurbits
Corn (and
Lily family other
grains)
14. 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
16. Earwigs
• Trap in tuna cans baited with
fish oil or bacon grease. Trapping is very effective against earwigs.
• 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.
17. Lady beetle lunching on aphids
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.
18. 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.
19. Beet Armyworm
• Attracted to
lettuce, cabbage, beans, peppe
rs, tomatoes, spinach, onion, b
eets
• 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.
20. 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
21. 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.
22. Spider mites
• Found on undersides of leaves;
webbing sometime present.
• Manage dust build-up on
Spider mite stippling on eggplant leaves
leaves.
• Life cycle of only 7 days!
• Spray with insecticidal
soap, horticultural oil, or neem
oil.
• Malathion for severe cases
• Overuse of pesticides destroy
spider mite predators.
• Attack:
melon, raspberry, eggplant, be Source: Utah State University Cooperative Extension
ans, etc.
24. 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
Like stink bugs, squash bugs give off plant.
an unpleasant odor when crushed.
• Insecticides provide only
temporary control.
25. • Control weeds, esp. Russian
thistle, common
Stink bugs mallow, mustards.
• Adults overwinter on the
ground under leaves – remove
debris at the end of the
Stink bug damage on tomato fruit growing season.
• Insecticidal soaps are effective.
Note the shield shape of the body.
26. 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.
27. 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.
28. 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 Water your beds before covering with plastic.
for best effect.
▫ Seal edges with bricks or dirt.
29. 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.
30. Flixweed
Winter Annual Weeds
• Germinate in fall/winter.
• Flower and set seed in spring.
• May reseed themselves before
fall crops are planted.
Redstem filaree
Prickly lettuce
Common mallow
32. Perennial Weeds
Some have food storage organs that sprout new
shoots.
tuber
Johnsongrass Yellow nutsedge Dandelion
Sedges
33. 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.
34. 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.
35. 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.
36. 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.
37. 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.
38. Purslane (Portulaca oleracea)
• Summer annual
• Fleshy, grows as a low Purslane is edible!
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.
39. 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.
40. 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.
41. 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.
42. Wildlife in your garden -mammals
• Legal status:
▫ Game species
▫ Furbearing
▫ Protected, sensitive or
threatened
• Management guidelines:
▫ Hunting
▫ Trapping
▫ Baits /rodenticides
▫ Exclusion
43. Exclusion
• Eliminate access.
• Install barriers when animals
are away.
• Use fine mesh wire to protect
plants.
• Repair holes in fences.
44. 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
45. 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 noncrop
areas.
• Clear weeds and debris.
• Mesh cylinders for single
plants
• Natural predators: owls,
hawks, cats, dogs
46. 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
47. 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
48. Quail
• Game bird – need a permit to
hunt, capture or kill.
• Scare tactics – flashers
• Exclusion
49. 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
Hinweis der Redaktion
Integrated pest management can be used for control of any landscape pest, including insects, disease, and weeds. The key to an effective integrated pest management program is regular monitoring to detect the pest when it first becomes active. Once the pest has been detected, you start with the least toxic method of control to keep the numbers of pests within tolerable limits. In the natural world, insects, disease, and weeds are not absent – they are simply kept in check by the natural conditions and predators that have evolved along with other plants. Left undisturbed, such a landscape will remain healthy and productive indefinitely. Our built and managed landscapes have no such built-in controls. But it is possible to build them in ourselves given knowledge about potential problems and armed with tools and a system for knowing when and how to use them – this is the essence of IPM.
In the system of integrated pest management, a variety of tools are available for control of pests. What distinguishes this system from randomly searching for a way to respond is the emphasis on use of tools that cause the least harm first, only resorting to more powerful (and toxic) methods if other methods don’t work. Using IPM puts you in control. Instead of reaching for a pesticide the moment you see a problem, you first examine the circumstances and select the most appropriate control. Types of control are in three categories: nonchemical – including hand-collecting of insect pests or pruning of diseased limbs, biological – which might include planting resistant cultivars, use of natural enemies, or biologically-derived chemicals, and chemical – the use of traditional chemical pesticides.
Insects pass through several stages in the maturation process. This egg-larva-pupa-adult sequence is common to many insects, but some go through an egg-nymph-adults sequence. Insects in the larva stage are often called worms, caterpillars, or grubs. Damage from insects is almost always due to either chewing or sucking, and this occurs at various stages of their maturation, depending on the species. Similarly, insects are more vulnerable at various stages of their development, and we can use this to time our control of these pests. Insects are usually most vulnerable when they are actively feeding or moving about the plant. Insects are not vulnerable in the pupal stage. Similarly, pests that gets into the flower or fruit as larvae are difficult to access; they must be controlled in the first hatch stage or in the adult before eggs are laid. IPM relies on exact timing and, therefore, minimal use of chemicals to control pests.
One of the best defenses against pests is healthy plants – prevention of problems before they occur. Proper cultural practices, such as fertilizing and watering in an appropriate manner can keep pests from doing major physical damage to plants. Proper pruning with sharp implements and pruning cuts designed for rapid wound healing will prevent entry by disease organisms or insects. Pruning also opens up the plant to air circulation to prevent many diseases. Avoiding over- or under-watering is also important. Over-watered plants, especially those in heavy clay soils, are more susceptible to root rot diseases due to lack of oxygen in the root zone. Under-watering can cause stress to plants that may become more vulnerable to insects like borers. Powdery mildew and spiders mites are attracted to dry, dusty foliage, and many plants benefit from an occasional spraying to keep foliage clean and moist. However, this type of spraying should be done early in the day to avoid water sitting on leaves overnight, which can lead to other kinds of diseases. Making sure plants are vigorous and healthy keeps their defense against many pests strong. However, leaf-sucking insects like aphids are attracted to high-nitrogen sap in over-fertilized plants so make sure not to over-do it. Crop rotation helps with vegetable plants by rotating the type of crop from year to year that is planted in any one area – to prevent build-up of insects or disease organisms attracted to that crop.
Physical controls are another good way to prevent problems before they reach threshold conditions. Insects in their caterpillar or adult stage are often easy to see and may be removed by hand if the numbers are low. Barriers like fences and chicken wire can be used to prevent damage by rodents and other small animals. Sticky tree bands are used to create a barrier to insects that may crawl up the trunk to gain access to the plant – they work for carpenter ants, cankerworms, and gypsy moths in their larval stage. Pheromone traps lure insects in with a chemical sex attractant (the pheromone). Some insects are attracted to colors like yellow or blue – sticky cards in those color trap the insects. This can be used to control insect numbers, but is also used as a way of monitoring so you can identify which pests are present and know when the threshold for control has been reached. Rogueing is a term used to describe removal of plants that are diseased or insect-infested to prevent further spread.
Natural enemies are insects that prey on other insects, some of which are pests on landscape and garden plants. We can learn to encourage their presence in our gardens by recognizing them and minimizing use of broad-spectrum controls that eliminate beneficial insects along with the pests. We can also plant wildflowers that attract and provide food and shelter for them. Insect predators can also be purchased for you to release in your landscape if needed. Good predators of insect pests include parasitic wasps, lady bugs (or beetles), lacewings, praying mantids, predator mites, and parasitic nematodes. Some predators, like lady bugs, attack a wide range of insect pests; however, others are more specific to their host – like predatory mites that attack spider mites. If you decide to purchase predators, remember that they are living organisms that cannot be stored until needed. It’s important that you have a good program of monitoring in place, and that you learn to recognize insects common to your area, so you know what kinds of predators will be needed to do the job.
Braconids are a family of parasitoid wasps that are very specific in their choice of hosts. A good example is Cotesiacongregatus. Less than 1/8 inch long, black with yellowish legs and clear wings, this tiny wasp attacksthe tomato hornworm.The female wasp uses her ovipositor to lay eggs just under the skin of thehornworm. As the eggs hatch, the larvae feed on the hornworm’s viscera – literally eating the hornworm alive. Larvae chew their way out through the host’s skin when they mature. Once outside, the future wasps pupate, spinning tiny whiteoval cocoons along the external back and sides of the worm. When the adult wasps emerge from the cocoons, the already weakened hornworm will die, thus preventing any further defoliation on tomato plants. Another common beneficial insect is the lady beetle. Everybody recognizes the lady beetle, but because lady beetle pupae do not resemble the adults,many gardeners assume that lady beetle pupae are pests. Consequently, these pupae are squashed or scraped off and destroyed. Each lady beetle larva eats many aphids and other pests, and each lady beetle lays many eggs which would hatch into many more larvae. Each pupa destroyed allows thousands of aphids to survive. Learn to recognize beneficial insects in your garden!
Microbial pesticides, such as Bacillus thuringiensis(Bt) and Talaromycesflavusact against specific pests. For example, one form of the bacterium Bt is used to control many insects in their larval or caterpillar stage; e.g., spruce budworm, cabbage looper, and gypsy moth. It works by attacking the lining of their stomach. Taloromycesflavusis a fungus which attacks other soil fungi, including the fungi that cause wilts in some ornamentals and vegetables. Microbial sprays generally do not kill beneficial organisms. Insecticidal soaps reduce populations of soft-bodied insects, such as aphids and mites, by dissolving the waxes that coat their bodies causing them to dry out. Horticultural oils work by smothering insects; they also disrupt the metabolism of insect eggs. Good control requires treatment of insects during a vulnerable stage, like during the crawler stage for scale insects. Horticultural oils should not be used when temperatures are above 90 deg F or below 32 deg F. Botanical pesticides include chemicals derived from common plants that are effect against certain pests. Rotenone is a chemical derived from the roots of tropical legumes. It is dusted on a plant and inhibits cellular respiration of insects. Long sleeves and a mask should be used when dusting this product. Neem oil comes from the neem tree. It acts as a growth regulator interrupting the insect’s growth cycle. Insects are most vulnerable at the larval stage. Pyrethrum is derived from the chrysanthemum. It controls a wide range of insects and should not be confused with the more toxic pyrethroid insecticides. Insecticidal soaps, horticultural oils, and botanical pesticides are safer than man-made chemicals, but they can kill beneficial insects as well as the pest if they are in the path of the spray. However, they will not harm those that move in after treatment.