More in Gardening

Working the Bugs Out

Here's a safe and effective system to control the plant-eating pests in your yard.

Grasshopper
Photo by Dwight Kuhn
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Grow plants in your yard, and you're bound to have pests. There's no way around that, but how you deal with the critters is changing. A decade ago it was common to reach for potent bug sprays that killed — indiscriminately — as soon as the creepy crawlers were sighted. But with increasing concern over chemicals in the environment, there are now safer ways to manage pests in our yards. The system is called integrated pest management, or IPM. This commonsense approach relies on the least toxic methods to keep bugs from devouring plants. IPM begins with preventing pests in the first place. It then proceeds to using traps, barriers and helpful insects and, finally, pesticides that are not as toxic as some used in the past. The idea is to keep pests at manageable levels, not to wipe them out completely. You don't have to be an expert to make IPM work, but you do need to know something about your plants and their pests, and then weigh the best solutions.
Grow plants in your yard, and you're bound to have pests. There's no way around that, but how you deal with the critters is changing. A decade ago it was common to reach for potent bug sprays that killed — indiscriminately — as soon as the creepy crawlers were sighted. But with increasing concern over chemicals in the environment, there are now safer ways to manage pests in our yards. The system is called integrated pest management, or IPM. This commonsense approach relies on the least toxic methods to keep bugs from devouring plants. IPM begins with preventing pests in the first place. It then proceeds to using traps, barriers and helpful insects and, finally, pesticides that are not as toxic as some used in the past. The idea is to keep pests at manageable levels, not to wipe them out completely. You don't have to be an expert to make IPM work, but you do need to know something about your plants and their pests, and then weigh the best solutions.
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Snails and harmful pests
Photo by Dwight Kuhn
Slugs/Snails

Description: Soft-bodied, legless soil dwellers with shells (snails) or without shells (slugs)

Where: Found in moist, shady
areas throughout North America. Hostas and fruits are favorite plants

Damage: Chew holes in leaves; leave slime trails

Controls: Use drip irrigation to keep garden drier. Also try Sluggo and Escar-go baits, copper barriers around individual plants, diatomaceous earth, saucers of beer and trap boards. Toads, snakes, ducks and geese feed on slugs
Prevention You can stop a lot of pest problems by growing hardy, well-adapted plants. Putting the right plant in the right place allows it to grow strong and thwart insect attack. A plant that languishes, for whatever reason, is ripe for pest problems. To find plant information, check the plant label or a reference book, or ask a nursery professional or consult your local extension service. Basically, you need to know the sun or shade tolerance, moisture preference and soil requirements of plants in your yard. If you have a plant growing where it shouldn't be, consider removing it or transplanting it to a more suitable location.
Mix It Up
Large expanses of a single type of plant invite pest feeding frenzies, so you should grow a variety of plants. Instead of a solid privet hedge, for instance, consider smaller clusters of viburnums, chokeberries, barberries, or similar shrubs hardy in your climate. And rather than using uniform plantings of yews along the foundation, intersperse spireas, weigelas and other flowering shrubs. These multiplant arrangements reduce pest problems and also look more interesting.
Welcome the Good Guys
Encourage beneficial insects — the ones that kill bad bugs — by growing plants these insects are drawn to for food and shelter. Particularly desirable plants are members of the following families: carrot (dill, parsley, fennel); daisy (coneflower, coreopsis, zinnias); and mustard (sweet alyssum, basket-of-gold alyssum and, when allowed to flower, broccoli).
Keep the Garden Tidy
Weeds provide good breeding grounds for insect pests. Keep them mowed to prevent unwanted bugs from moving into your yard.
Keep an Eye on Plants
Inspect suspicious areas, and destroy severely infested plants. It makes sense to sacrifice a single marigold crawling with spider mites before the pests engulf the entire planting. Taking weekly observational strolls through the garden will help you nip problems in the bud before they become epidemic.
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June beetle larvae and harmful insects
Photo by Dwight Kuhn
Lawn Grubs

Description: May/June beetle adult is reddish brown to black with hard shell; Southern masked chafer adult is light brown; Northern masked chafer adult is chestnut brown. Larvae of all are 1-inch long, white, C-shaped grubs

Where: May/June beetle found throughout North America. Southern masked chafer in Midwest and Southeast. Northern masked chafer in Northeast. Larvae live in soil under turfgrass

Damage: Adults of May/June beetle chew foliage of oak, willow, apple, poplar and birch trees. Most damage from larvae comes from their chewing on grass roots; turf turns brown from lack of roots in summer

Controls: Predatory nematodes (Steinernema and Heterorhabditis, Grub Guard, Grub-Away) mixed with water and applied to soil
Physical Controls
Small-scale infestations can be squelched by simply removing pests like chewing caterpillars, slugs, or Japanese beetles from the plant. (Use rubber gloves if you're squeamish.) Blast spider mites and aphids with a garden hose. Most won't ever find their way back to your plant. Simple barriers can keep some pests at bay. Protect new flower and vegetable transplants from cutworms by surrounding stems with a protective paper collar. Keep slugs away from choice hostas by encircling plants with a copper strip in contact with the soil. Traps are effective at controlling some pests. Slugs and adult weevils congregate under boards placed on the ground. Slugs also are attracted to saucers of beer buried in the soil to the rim. Red balls coated with Stikem Special or Tangle-Trap attract and trap apple fly maggot adults, preventing them from laying their eggs in real apples.
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spider mites and harmful insects
Photo by Ronn West
Spider Mites

Description: Reddish-brown or pale, tiny, eight-legged. Often
produce webbing more visible than the mites themselves

Where: In dry areas throughout North America. Common in warm locations; most often on leaf underside. Roses, beans and marigolds are favorites

Damage: Suck plant juices from leaves. Create silvery stippling on leaf; leaves yellow and brown; webbing

Controls: Forceful water spray, insecticidal soap, horticultural oil, lacewings, ladybugs, predatory mites (Galandromus, Phytoseiulus), neem, sulfur dust.
Biological Controls
Researchers have figured out ingenious ways to manipulate natural controls to reduce pests. Some traps use pheromones, the natural perfume that pests use to find each other and mate. Codling moths and peach tree borers can be controlled with pheromone traps. But be cautious about using Japanese beetle pheromone traps. They draw the beetles to the general area but not necessarily into the trap. The result is an increase in Japanese beetles rather than control. The traps can be useful, however, in large yards when they are placed far away from prized plants. Numerous beneficial insects are available commercially at nurseries, by mail and on the Web. But you'll need to persuade these insects to stay in your garden so they don't all fly away shortly after release. Ladybugs, for example, are more apt to stay when you release them in the evening, dispense only a couple per square yard and spray plants with a sugar-water solution to mimic the honeydew secreted by aphids, their favorite taste treat. Another example of beneficial insects are parasites that kill pests by laying eggs inside the pests' body. After the eggs hatch, the larvae eat the pests from the inside out. Not a pretty picture, but it works in the garden. Millions of parasites occur naturally, and you'll find a few available commercially. Most common are tiny wasps called trichogramma. They lay their eggs in moth and butterfly eggs that become plant-chewing caterpillars. These wasps are perfectly harmless to people and animals. Also available commercially are parasitic nematodes that target insects which spend part of their life below ground. Lawn grubs, Japanese beetle larvae and weevil larvae are examples of pests nematodes control. Nematodes work best in loamy soil in mild climates. They are least effective in extremely sandy or clay soils, in dry areas and at extreme temperatures. You'll find them sold in either in a paste form or on a sponge, under such names as Grub-Away and Grub Guard. Mix with water and spray on moistened soil or lawn. Insects, like humans and other animals, get diseases. Some disease-causing organisms are sold to gardeners to target specific pests. Bacillus thuringiensis (B.t., Dipel, MVP), a bacterium that paralyzes the gut only of plant-chewing caterpillars, is one of the most widely available. Another is milky spore, which attacks Japanese beetle larvae but not the adults.
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Gypsy moth laying eggs and harmful insects
Photo by Dwight Kuhn
Gypsy Moth

Description: Adult female is a creamy white moth; male brownish moth. Larvae are black hairy caterpillars with five pairs of blue spots and six pairs of red spots on back. Egg masses are buff-colored

Where: Throughout Northeastern U.S.; isolated elsewhere. Egg cases are laid everywhere. Larvae feed on the foliage of shade trees

Damage: They defoliate trees by chewing leaves; oaks are a favorite

Controls: Handpick and destroy egg masses; spray B.t. when larvae are young
Using Pesticides
A number of different "organic" and "natural" pesticides are available. But keep in mind that organic products aren't always the least toxic. For instance, nicotine sulfate (Nico soap), a tobacco-derived insecticide, is five times more toxic than carbaryl (Sevin), a common chemical pesticide. In IPM, applying any kind of pesticide is the last resort. Pesticides made from plants. The most common is azadiractin (neem, BioNeem). Most are only moderately toxic and break down relatively quickly, though they can cause unwanted damage. For example, neem is useful because it kills a wide range of insect pests, including aphids, whiteflies, mites and fungi, but it also kills beneficial insects, such as bees. Don't apply it to blooming plants while bees are active. In addition to killing them, neem repels bugs, preventing reinfestation.
Insecticidal soap. Common examples are M-Pede and Safer Insecticidal Soap. The soap kills a number of soft-bodied insects, such as aphids and mites. Because the soap works on contact, it must be sprayed directly onto the pest. You can buy insecticidal soap in a ready-to-spray form or as a concentrate; hard water reduces the effectiveness of the soap. Don't substitute household liquid soaps for insecticidal soap because they can damage plants.
Horticultural oils. These oils have long been used to control pests on dormant woody plants. Now, you can get the desired smothering effect of oil during summer growing season by using highly refined summer oils (Sunspray Ultra-Fine Oil) or non-petroleum-based insecticidal oils (Natur'l Oil, Oil-Away). These oils control aphids, beetles, mites, scales, lace bugs and mealybugs.
Also consider these additional products:
• Garlic Barrier repels insects but doesn't kill them. It must be applied frequently, before bugs arrive in your garden.
• Sulfur is useful to control fungal diseases and suppress mites. It's sold in a concentrated liquid or powder form.
• A new mineral product, iron phosphate (Escar-Go, Sluggo) is made into a bait for snails and slugs. The pests stop eating several days after taking the bait, and soon die. The product is safe for use around pets and wildlife.
Remember, the presence of pests in your yard doesn't mean they'll destroy your plants. The key is to keep pest numbers down. Start with healthy plants and good gardening practices and you'll have success without waging chemical warfare.
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two Japanese beetles on a leaf
Photo by Dwight Kuhn
Japanese Beetle

Description: Adults are metallic green with coppery wing covers; larvae are grayish-white grub

Where: Concentrated in eastern third of U.S.; less common elsewhere. Adults feed on foliage of more than 300 species of trees, shrubs and flowers; larvae in soil

Damage: Adults chew leaves and flowers of plants; larvae feed on roots

Controls: For larvae: Milky Spore or nematodes (Grub Guard, Grub-Away). For adults: neem or rotenone; place Japanese beetle pheromone traps outside garden, not near plants attractive to the beetle
Where to Find It: Arbico Environmentals
Box 4247
Tucson, AZ 85738-1247
www.arbico.com
800-827-2847
The Bug Store
113 W. Argonne
Kirkwood, MO 63122
www.bugstore.com
800-455-2847
Gardener's Supply Co.
128 Intervale Rd.
Burlingtion, VT 0501
www.gardeners. com
800-955-3370
Gardens Alive!
5100 Schenley Place
Lawrenceburg, IN 47025
www.gardens-alive.com
812-537-8651
Peaceful Valley Farm Supply
Box 2209
Grass Valley, CA 95945
www.groworganic.com
916-272-4769
Further reading: The Gardener's Guide to Common-sense Pest Control
by William Olkowski, Sheila Darr and Helga Olkowski
Taunton Press
Newtown, CT
1996
300 pages, $19.95.
Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide
by Steve H. Dreistadt
University of California Division of Agriculture and Natural Resources
Oakland, CA
1994
327 pages, $32.
Pests of the Garden and Small Farm: A Grower's Guide to Using Less Pesticide
by Mary Louise Flint
University of California Press
Los Angeles, CA;
1999
288 pages, $35
Pests of the West: Prevention and Control for Today's Garden and Small Farm
by Whitney Cranshaw
Fulcrum Publishing
Golden, CO
1998
224 pages, $19.95
On the Web: Biocontrol Network Reference Center
www. biconet.com/reference/BICONETRC.html Entomology and related Web sites
entweb.clemson.edu/entsites Ohio State University
www. ag.ohio-state.edu/~ohioline/ lines/pests.html
 
 

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