Manage Pests A healthy garden hosts abundant life, including insects and wildlife. Most of these share the garden without causing probl~ms. Many are welcome visitors, performing vital functions such as pollinating plants; feeding on undesirable insects; and helping to break down plant matter, building soils and recycling nutrients. But some are pests that feed on and i'njure plants.

Approach pests with Integrated Pest Management (IPM), a philosophy whose primary aim is prevention, IPM uses biological, cultural, and physical controls to help avoid serious insect, disease, and other pest problems and to reduce pests' effects to tolerable levels. Chemical controls using pesticides are employed only as a last resort.

IPM begins with good cultural prac­tices. Choose plants that are adapted to your climate and garden conditions. Buy varieties that are resistant to diseases or unpalatable to pests. Prepare plant­ing beds well, and periodically amend the soil with organic matter to improve conditions for root growth. Water and fertilize appropriately to promote healthy

NATURAL PESTICIDES Natural pesticides are products whose active ingredients originate in a plant, animal, or mineral, or whose action results from a biological process. "Natural" does not mean harmless; some natural products can still harm people, pets, or plants if they are used incorrectly, and most of them will kill beneficial insects along with the pests.

When using any pesticide, read the label carefully and follow the manu­facturer's directions exactly. The label will clearly state the plants and pests for which the control can be used.

Bacillus thuringiensis (Bt) is a naturally occurring bacterium. Several strains exist; each targets different kinds of insects. The most common, Bt kurstaki, controls leaf-feeding caterpillars.

. Diatomaceous earth (DE) is a powdery substance made from the skeletons of microscopic marine organisms. It damages the protective coats of invertebrate pests such as ants, slugs, and snails, but must be kept dry to be effective. Use the horticultural product, not the one intended for swimming pool filters. Wear a mask during application.

Food-grade oils and extracts are commercial versions of homemade repellents and pesticides that gar­deners have relied on for centuries. Active ingredients include citrus peels, garlic, and hot pepper. Effectiveness varies.

Horticultural oils are typically highly refined petroleum oils. Botanical oils are derived from plants, such as citrus peels or seeds of neem or soybean. Oils act on con­tact by smothering aphids, mites, whiteflies, scales, and other insects. Do not apply oils when plants are under drought stress and tempera­tures are high.

Insecticidal soap is made from potassium salts of fatty acids from plants and animals. Soaps work on contact against aphids, mealybugs,

plants. Check plants frequently to spot problems before they get out of hand.

1 PHYSICAL CONTROLS . ,

Physical controls include actions that directly kill, deter, or capture pests.

Handpick to~estroy snails, cater­pillars, insect egg masses, and other pests that you find among the plants. Take care to leave the lady beetle larvae and other beneficial insects that are sometimes mistaken as pests.

Prune and destroy branches, canes, and other plant tissues that show evi­dence of actively developing pests such as borers, scales, or fire blight, and any plant diseases.

Spray plants with a strong jet of water to dislodge or kill small insects suth as aphids, thrips, and spider mites.

mites, scales, thrips, and whiteflies. Hard water inactivates the soap, so . mix the concentrate with soft water, distilled water, or rainwater. Avoid using dish detergents.

Neem oil (Azadirachtin) is from a tropical tree (Azadirachta indica). Effective against aphids, beetles, caterpillars, mealybugs, mites, thrips, whiteflies, and powdery mildew.

Pyrethrins are derived from the dried flowers of Tanacetum cinerariifolium. Lethal to many pests. They break down quickly in sunlight; apply after sundown.

Spinosad is made from the extracts of a soil microbe, Saccharopolyspora spinosa. It controls caterpillars, thrips, and some beetles and sawflies. Although relatively selective, it kills some beneficial species.

Sulfur is dusted Ol' sprayed over plants to control mites and psyllids as well as some plant diseases. Do not use in conjunction with horticultural oils or when air temperature is above

85°F (29°C).

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Barriers deter pests. These may range from a high , continuous fence around an entire garden to row covers protecting a bed of plants.

Repel pests, such as aphids , thrips , and whiteflies , by planting through reflec­tive, foil-like mulch.

Rotate the location of plants in your garden from season to season. This is particularly helpful for reducing plant diseases and root-feeding insects.

Trap to capture and monitor pests. Look during the day under pots or trap boards, and scrape any snails or slugs into a bucket of soapy water. Yellow sticky cards can capture flying insects such as whiteflies and aphids. Damp newspaper or other cover can concen­trate slugs and earwigs that seek day­time shelter. Adults of some moths can be captured with pheromone traps that include as a lure the chemicals used by the female moth to attract a mate. Such traps are particularly useful in helping you know when to spray for fruit insects, such as codling moth in apples.

2 BIOLOGICAL CONTROLS

Every garden has a homegrown army of pest controls-predators , parasites , and beneficial pathogens that feed on garden pests; six garden "good guys" are profiled at right. To help increase beneficial populations , avoid using per­sistent pesticides and grow a diversity of plants. Many of these beneficia Is can be encouraged by planting flowers that provide nectar and pollen . Birds , toads , and garter snakes all prey on insects .

Spiders all feed on insects and can provide tremendous benefits in plant protection. Other insects , such as para­sitic wasps and tach inid flies , lay eggs onto or inside of pests; as the larvae develop, they kill the pest.

Parasitic nematodes are microscopic ~oundworms that kill insects through Introducing a bacterium into their body. Nematodes (which generally must be mail-ordered and applied) can help con­trol pests th~t spend part of their lives In the soil, such as white grubs, root Weevils , and cutworms.

Lacewing

Assassin bugs. Slim %-%-inch­long insects; may be red, black, brown, or gray. They feed on a wide variety of pests.

Lady beetle

the larvae, which resemble %-inch­long alligators, devour aphids, leaf-hoppers, and thrips, as well as mites. Larvae are commercially available.

Damsel bugs. Dull gray or brown, Lady beetles. Adults and their lar-. . %-inch-long, very slender insects vae (which look like %-inch-long alii-

with long, narrow heads. Nymphs gators) feed on aphids, mealybugs, resemble the adults but are smaller and insect eggs. You can buy the and have no wings. Both nymphs aphid-eating convergent lady beetle,

and adults feed on aphids, leafhop- but these must be released repeat-pers, and small worms. edly and most soon fly away. Freeing

them in large numbers at night after Ground beetles. Shiny black, 1

/2- first wetting foliage may encourage 1-inch-long insects. The smaller spe- them to stay a while. cies eat other insects, caterpillars, cutworms, and grubs; some larger Trichogramma wasps. These species prey on slugs and snails and very tiny parasitoid wasps attack their eggs. the eggs of caterpillar pests. Com­

Lacewings. The adults are 1-inch­long flying insects that feed only on nectar, pollen, and honeydew; but

mercially available species are adapted for gardens or for fruit trees. Because they are short-lived, repeated releases may be needed.

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730 PROTECT: MANAGE PESTS . . '

PLANT PESTS (continued)

3 SYNTHETIC PESTICIDES

PEST

Scales

Classified as "armored" (hard) or soft. In spring or summer, young scales ("crawlers") emerge. Adult scale insects have a waxy, scalelike covering. As scales suck out plant juices, yellow spots appear on foliage, and leaves may drop off. If the infestation is left unchecked, the whole plant turns sickly and stunted.

Snails and Slugs

Night-feeding mollusks. Snails have shells; slugs do not. Both feast on the seedlings and leaves of many plants. They hide by day, though they may be active on gray or rainy days. Regularly search their day-hiding places and crush them or scoop them into soapy water.

Thrips

Tiny, elongated insects that suck plant tissue : In heavy infestations, both flowers and leaves are dis­colored and fail to open normally. Leaves may take on a silvery or tan cast. Greenhouse thrips feed in a group and leave small black droppings on leaves.

Whiteflies

Adults are tiny white pests that fly up in a cloud when disturbed. The nymphs and adults suck plant juices from leaf undersides. Foliage may show yellow stip­pling , curl, and turn brown. Some kinds transmit plant virus diseases.

MANAGEMENT

Difficult to control. Encourage lady beetles and para­sitic wasps that kill scales. Control ants (see page 728), which often protect soft scales. Horticultural oil and insecticidal soap will help control crawlers, as will appropriately labeled synthetics. If applied early before the problem gets bad, imidacloprid is effective,against some types, but it does not control armored scales.

Minimize garden clutter and keep organic litter and mulch back from plants during wet weather. Trap and dispose of pests. Wrap copper strip barriers around raised beds and tree trunks. Keep the copper clean. Set out shallow containers filled with beer to drown the pests. Use bait containing iron phosphate. (Baits containing metaldehyde are a hazard to pets.)

Use row covers or reflective mulches before plants become infested . Clip off and destroy infected plant parts. Encourage beneficials. Spray with insecticidal soap, horticultural oil, pyrethrins, spinosad, neem, or appropriately labeled synthetics, including systemics.

Use floating row covers and/or reflective mulch before plants are infested. For greenhouse infestations, release Encarsia formosa, a predatory wasp, or use sticky yellow traps. Spray leaves with strong jets of water, insecticidal soap, oils, or neem. lmidacloprid can be effective.

Many of the older synthetic insecticides have been removed from the market due to environmental contamination and con­cerns about their effects on animals and human health. They have been replaced w~th pesticides of natural origin (see page 726) and with new classes of syn­thetic pesticides, such as neonicotinoids and pyrethroids (bifenthrin, permethrin, cyfluthrin , and esfenvalerate).

Some synthetic pesticides applied to the soil are absorbed by roots and moved systemically throughout the plant. Pesticides formulated as baits (combined with an attractant) can be particularly selective in their effects.

Systemic insecticides that are absorbed by the plant and moved with its tissues include acephate , an organo­phosphate , sprayed onto nonedibles only. Neonicotinoids (such as imidaclo­prid) include some that can be used on edibles (check label), and are applied to soil as a granule or liquid and absorbed by roots. Some formulations can also be applied to the foliage.

Store pesticides where they can be locked away from children and pets and separate from food. Buy only the amount that you need, and never mix more pesticide solution than you need. Never pour pesticides down the smk the toilet, or a storm drain , as this w 1 pollute surface waters. The only legal way to dispose of pesticides is to ta e them to your local household haz d ous waste facility. Only complete Y empty home-use pesticide conta e s may be disposed of in the trash. C tact your city or county publ ic 0 s department or your local was e 5

posal company for informatio ·

While natural pesticides degrade quickly, these insecticides kill insects that contact or eat sprayed foliage for days or weeks after their application . They are more toxic to beneficial insect pollinators, predators, and parasites, and some cause problems due to con­tamination of surface waters.

These systemics are mostly effective as long-lasting preventatives, applied before pests are established. To protect beneficial insects, do not apply system­ics prior to or during bloom.