In an attempt to stem the spread of the sweetpotato whitefly, now devastating agricultural crops in California's Imperial Valley, scientists at the University of California, Davis, have provided valley farm advisors with a tiny black beetle that is a natural predator of the whitefly. Some 200 of the pinhead-sized Delphastus pusillus black beetle -- a tiny cousin of the common lady bug -- were sent down to the Imperial Valley by Michael P. Parrella, a professor and chair of the UC Davis entomology department and postgraduate research scientist Kevin M. Heinz. The researchers added the Florida black beetle this fall to their laboratory, where for the past five years they have been searching for the best combination of biological controls for the sweetpotato whitefly. The black beetles were sent in late Ocober to Eric T. Natwick, a UC farm advisor and entomologist for Imperial County. "We sent the black beetle down to see if it could handle the hot desert temperatures," said Parrella. "So far it has survived and multiplied in cages and has dramatically eased the whitefly damage to cauliflower and broccoli in the fields." Parrella began studying biological controls for the sweetpotato whitefly several years ago in order to control the pest in poinsettia greenhouses. The tiny fly, believed to have originated in the Middle East, was introduced into the United States via shipments of ornamental plants to Florida, Parrella said. It has since spread into commercial greenhouses in Arizona and California, and has made its way into desert field crops. The whitefly has already destroyed the Imperial Valley's $22 million melon crop, and total agricultural losses are expected to top $200 million, according to Parrella. "What is particularly disturbing is that we are seeing the sweetpotato whitefly moving into crops on which it hasn't previously been found," he said. "It's attacking citrus, grapes cauliflower, broccoli and alfalfa." More than 2,000 whiteflies per square inch are being found on the leaves of the Imperial Valley field crops, Parrella said. At that rate, the pest is literally eating the crops alive. An additional concern is that the sweetpotato whitefly carries plant diseases, so plants that are not physically destroyed could be lost to disease. "The sweetpotato whitefly is a very efficient carrier of plant viruses," Parrella said. "When it feeds it appears to inject a toxin into the plant that results in a condition called silverleaf in squash and irregular ripening in tomatoes." Unlike many agricultural pests, the sweetpotato whitefly cannot be controlled with chemicals, due to an extremely high level of pesticide resistance. "We're encouraged, however, because the black beetle feeds on the whitefly eggs and immature stages," he said. "We expect to eventually go for a one-two punch using the black beetle and a parasite that will control the later stages of the whitefly." Parrella hopes that his laboratory's work in studying and rearing predators and parasites of the sweetpotato whitefly will be useful in the field. He is cooperating with researchers at UC Riverside and with farm advisors in the Imperial Valley. "We're not doing anything magical," he said, "but hopefully our five years of experience will be helpful in preventing the growth and spread of the sweetpotato whitefly infestation."