Grow Your Own, Nevada! Fall 2011: Controlling Pests


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  • 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.
  • Grow Your Own, Nevada! Fall 2011: Controlling Pests

    1. 1. Controlling Pests in Your GardenHeidi KratschUniversity of Nevada CooperativeExtension
    2. 2. Pests common in northern Nevada• Insects (many different kinds!)• Weeds• Rodents (and other unwanted varmints)• Diseases (rare, mostly caused by cultural problems)
    3. 3. 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.
    4. 4. 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
    5. 5. 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.
    6. 6. 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.
    7. 7. 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
    8. 8. Natural Predators• Assassin bugs• Parasitic wasps• Lady beetles• Lacewings• Snake flies• Praying mantis• Syrphid flies• Spiders
    9. 9. ExamplesTomato hornworm parasitized by aBraconid wasp - the white cocoonshouse the larvae that will emerge as Lady beetle larva attacking andadult wasps. eating aphids on a leaf
    10. 10. 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.
    11. 11. 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 enter4. Caterpillar dies of severe bacterial infection within 2 days.- Safe for organic production.- Each strain is specific for a particular pest.
    12. 12. Cabbage family Legume Carrot family family Crop RotationNightshade family Scheme Cucurbits Corn (and Lily family other grains)
    13. 13. 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
    14. 14. Floating row covers• Block insects• Protect plants from cold/frost
    15. 15. 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.
    16. 16. Lady beetle lunching on aphidsAphids• 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.
    17. 17. 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.
    18. 18. 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.
    19. 19. 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
    20. 20. 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.
    21. 21. 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.
    22. 22. Squash bugs Vs. Stink bugs
    23. 23. 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.
    24. 24. • Control weeds, esp. Russian thistle, commonStink bugs mallow, mustards. • Adults overwinter on the ground under leaves – remove debris at the end of theStink bug damage on tomato fruit growing season. • Insecticidal soaps are effective. Note the shield shape of the body.
    25. 25. 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.
    26. 26. Weed control(don’t let thishappen to you!)• Weeds rob your cropsof water, nutrients andsunlight.• Identify what it is andcontrol it early.• Compost annualweeds that haven’tgone to seed.• Destroy perennialsweeds, esp. the roots.
    27. 27. 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.
    28. 28. 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.
    29. 29. FlixweedWinter Annual Weeds• Germinate in fall/winter.• Flower and set seed in spring.• May reseed themselves before fall crops are planted. Redstem filaree Prickly lettuceCommon mallow
    30. 30. Summer Annual Weeds Crabgrass Redroot pigweed Russian thistleLambsquarters Common purslane Spotted spurge
    31. 31. Perennial WeedsSome have food storage organs that sprout new shoots. tuber Johnsongrass Yellow nutsedge Dandelion Sedges
    32. 32. 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.
    33. 33. 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.
    34. 34. 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.
    35. 35. 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.
    36. 36. 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.
    37. 37. 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.
    38. 38. 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.
    39. 39. 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.
    40. 40. 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.
    41. 41. Wildlife in your garden -mammals• Legal status: ▫ Game species ▫ Furbearing ▫ Protected, sensitive or threatened• Management guidelines: ▫ Hunting ▫ Trapping ▫ Baits /rodenticides ▫ Exclusion
    42. 42. Exclusion• Eliminate access.• Install barriers when animals are away.• Use fine mesh wire to protect plants.• Repair holes in fences.
    43. 43. 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
    44. 44. 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
    45. 45. 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
    46. 46. 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
    47. 47. Quail• Game bird – need a permit to hunt, capture or kill.• Scare tactics – flashers• Exclusion
    48. 48. Questions?• Jon Carpenter, Environmental Scientist, NDOA (Wildlife Control)• Jeff Knight, State Entomologist, NDOA (Insect Biology and Control)• Sue Donaldson, Water Quality and Weed Specialist,• Heidi Kratsch, Horticulture Specialist,