
                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, August 11, 1994                   TAG: 9408110041
SECTION: CURRENT                    PAGE: NRV-7   EDITION: NEW RIVER VALLEY 
SOURCE: Joe Hunnings
DATELINE:                                 LENGTH: Medium

INSECT PREDATORS A NATURAL WAY TO ATTACK PESTS

Nature provides gardeners with helpers to control many insects that attack cultivated plants. Among these helpers are the predatory insects that feed on pest species. The following are common insect predators found in most gardens. They are also commercially available, in case gardeners want to try to increase their pest-predator population.

Ladybugs, or ladybird beetles, are probably the best-known insect predators. Many species of ladybugs occur naturally in the yard. Both adults and larvae of the beetles feed on soft-bodied insects. Aphids are their preferred food, but ladybugs also eat mealybugs and spider mites.

Adult ladybugs may be purchased from many sources. However, purchased ladybugs often will leave the release site unless properly conditioned by the insectary. Ladybugs can be encouraged to stay in a garden by releasing them in a screened cage over an aphid-infested plant for a while, or by releasing them after dark.

Green lacewing larvae (Chrysopa carnea) - known as aphid lions - are voracious predators on insect eggs, aphids, spider mites, thrips, leafhopper nymphs and small caterpillar larvae. The adult lacewings are not predacious, feeding instead on honeydew secretions of aphids. Both eggs and newly hatched larvae are available from insectaries. Lacewing eggs can be distributed in a garden using a salt shaker. Leaving some pest-infested plants with honeydew on them will improve lacewing reproduction.

Several species of predatory mites are available from insectaries, including Phytoseiulus persimilus, Mataseiulus occidentalis and Amblyseius californicus. These mites are excellent predators of many mite pests, including the two-spotted spider mite. Predatory mites are used quite successfully for biocontrol in greenhouses and interior environments. P. persimilus has been used for effective biocontrol of spider mites on strawberry fields in California at release rates of 70,000 to 90,000 P. persimilus per acre.

The mealybug destroyer (Cryptolaemus montrouzieri) is a Coccinellid beetle originally imported from Australia in 1892 to control mealybugs in California citrus groves. It is still used extensively for mealybug control in citrus trees and also for biocontrol of mealybugs in greenhouses, botanical gardens and Christmas tree farms. It can be used on houseplants; however, some plant owners are not comfortable setting beetles loose in their house.

The predatory midge (Aphidoletes aphidimyza) has been used successfully to control aphids in greenhouses and some outdoor environments. The adult midge is a small, black fly that lives only a few days. Eggs are laid on the underside of leaves close to aphid colonies, often beneath the aphids. The midge injects a paralyzing toxin into the aphid, and then, when the aphid has ceased struggling, it bites into the thorax and sucks out the body contents. Ant control in the greenhouse is essential before introducing Aphidoletes, since ants protect aphid colonies.

by CNB