A pinhead-sized wasp may help cotton plants battle one of their worst insect enemies, the cotton aphid. Scientists with the Agricultural Research Service have recruited the shiny black wasp, Lysiphlebia japonica (lye-suh-FLEA-bee-uh juh-PON-ih-cuh), for an outdoor experiment in California's San Joaquin Valley.

A female L. japonica wasp attacks the cotton aphid as the pest feeds. She jabs the aphid with her stinger-like ovipositor, then pumps a whitish egg into the doomed insect. The egg hatches and becomes a larva that feeds on the aphid's innards, killing it. Later, the wasp emerges as a winged adult.

L. japonica is harmless to humans and animals, according to ARS plant pathologist Raymond K. Yokomi at the Horticultural Crops Research Laboratory, Fresno, Calif. Yokomi is working with scientists at the ARS Western Integrated Cropping Systems Research Unit, Shafter, Calif.; the California Department of Food and Agriculture and the University of California Cooperative Extension Service. The California Cotton Pest Control Board funds part of the research.

To start their wasp colonies, the researchers used insects from ARS’ Horticultural Research Laboratory, Orlando, Fla., where scientists are scrutinizing the wasp's ability to fight citrus pests. Formerly at Orlando, Yokomi was first to import the Asian wasp into America for testing as a biocontrol. He and colleague Yuqing Tang at Orlando were first to determine how to raise it indoors for outdoor use.

The cotton aphid and other aphids cost California cotton growers more than $11 million in l996. Cotton aphids feed on sap and excrete sticky honeydew that contaminates cotton fibers. Sticky fibers may jam cotton gins or equipment at textile mills.

Scientific contact: Raymond K. Yokomi, USDA-ARS Horticultural Crops Research Laboratory, 2021 So. Peach Ave., Fresno, CA 93727-5951, phone (209) 453-3021, fax (209) 453-3088, e-mail ryokomi@lightspeed.net