UNIVERSITY PARK, Pa. -- For most people, the only good bug is a dead bug. But if your garden crops are being attacked by insects, an entomologist in Penn State's College of Agricultural Sciences says you should think twice before killing everything with six legs.

"Only 1 percent of insects actually are pests," says Lyn Garling, education specialist with the Pennsylvania Integrated Pest Management (IPM) Program. "Chances are that most insects you encounter are neutral as far as you're concerned. And probably at least 20 percent are, at some point in their lifetime, predators or parasites of other insects."

The difficult part, Garling says, is telling the good bugs from the bad. "When you walk through your garden, think of it as the African Serengeti," she says. "The pests generally are slow moving and eat leaves or fruit -- the cows of the insect world. The predators tend to be fast moving and quick, with large eyes to seek out prey. They are the lions of the insect world."

Garling says there are abundant beneficial organisms in most gardens. "Wasps, beetles, flies, spiders -- virtually all orders of arthropods have predators and parasites among them," she explains. "Probably the three most common beneficial insects in Pennsylvania are ladybird beetles, green lacewings and hover flies."

--Ladybird beetles, commonly referred to as ladybugs, are predators of aphids and other pests. Adults most often are red, orange or yellow with black markings. "Lady beetles in their larval stage are especially voracious," says Garling. "But most people would not recognize a ladybug larva, which has an alligator-like appearance."

--Green lacewings appear mostly in late summer. "They are generalist predators," Garling says. "Adults are pale green, with long antennae and large, transparent wings. The adults feed mostly on nectar and pollen, but their alligator-like larvae eat aphids, spider mites, small caterpillars and other insects, as well as a lot of eggs laid by pests."

--Syrphid flies, or hover flies, most commonly are yellow with brown or black stripes on the abdomen. "They look like a tiny bee, but they don't sting," says Garling. "Adults often hover around flowers and feed on pollen. The maggot-like larvae are especially fond of aphids."

Garling says to encourage beneficials, plan or modify the garden habitat to provide for their needs. "Like all wildlife, beneficial insects need food, water and shelter," she explains. "The best way to provide those things is to have a diversity of plants in your garden. You should plant a mixture of perennials, biennials and annuals, and make sure there's always something flowering. Flowers are a great source of energy for foraging predators and parasites.

"Also have a range of architecture among your plants -- tall, short, vine-like trailing on the ground -- because each provides a different habitat," she adds. "Establish mulched areas that provide a moist environment, and keep other areas dry and airy."

Purchasing beneficial insects for release in your garden is an option but may not be effective, according to Garling. "There are good companies that supply beneficials for the home garden," she says. "But you have to know the biology of the beneficial to be sure it's going to do what you want it to. For instance, if it's not pest-specific, it may go after other, more abundant pests and not take care of your particular problem. If you have a diverse habitat in your garden, most of the work is being done for you already, so you're probably better off augmenting the natural population you already have."

Garling recommends using caution when applying pesticides in your garden. "Traditionally, garden pesticides have been broad spectrum, meaning they will kill a wide range of insects, including beneficials," she warns. "Before using pesticides, be sure you know what pest is causing your problem. Always carefully read the label instructions, and try to apply the pesticide at a time when beneficial insects are least likely to be present. You also should consider insecticidal soaps, botanicals or other products that are less likely to affect beneficials."

For more information on the use and identification of beneficial insects and other IPM topics, Garling recommends the following books and Web sites:

--NCR Publication #481 "Biological Control of Insects and Mites" (for more information, call 608-262-3346)

--"Natural Enemies Handbook" (800-994-8849)

--"Natural Enemies of Vegetable Insect Pests" (607-255-2080)

--"Biological Control: A Guide to Natural Enemies in North America" (http://www.nysaes.cornell.edu/ent/biocontrol)

--USDA National Biological Control Institute (http://www.aphis.usda.gov/nbci/nbci.html)

--National IPM Network, North Carolina (http://ipmwww.ncsu.edu/)

--Pennsylvania IPM Program (http://paipm.cas.psu.edu/)

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EDITORS: For more information, contact Lyn Garling at 814-863-8884.

Contacts: Chuck Gill cdg5@psu.edu 814-863-2713 814-865-1068 fax