Don’t bombard cotton pests with insecticide; supplementing chemical sprays with biological control methods is a better approach.

That’s the advice of entomologists with the U.S. Arid-Land Agricultural Research Center and the University of Arizona. The center is a new facility of the Agricultural Research Service, the U.S. Department of Agriculture’s primary scientific research agency.

The silverleaf whitefly is a serious cotton pest. In the 1990s, at the peak of their population explosion, whiteflies were destroying millions of dollars’ worth of U.S. crops every year. ARS entomologists Steven Naranjo and James Hagler contributed to a national effort to reduce the whitefly population.

Now they advocate a combination of preventative action, biological control and selective insecticides as the most effective, environmentally friendly response to whitefly invasions.

Naranjo and University of Arizona researcher Peter Ellsworth analyzed the factors contributing to whitefly mortality. They identified the most common causes of death, including predatory insects and weather-induced dislodgment. This led them to recommend conserving natural predators for effective whitefly control.

Predators identified

To discern which insects are natural whitefly predators, Hagler developed an assay that tests insect gut contents for evidence of whitefly consumption. Using this method, he and Naranjo quantified predation frequency for 18 whitefly predators, many of which had been unidentified previously.

The researchers recommend complementing biological control with commercial insect growth regulators like buprofezin and pyriproxyfen. Their studies show that growth regulators tend to conserve natural predators, while conventional insecticides can be indiscriminate, eliminating predator and prey alike.

The scientists’ research has enabled them to make specific recommendations for improving whitefly population management. Their work is part of a growing knowledge base that has helped decrease insecticide use for whitefly control by about 85 percent since 1995.

Read more about the research in the April issue of Agricultural Research magazine, available online at: http://www.ars.usda.gov/is/AR/archive/apr06/whitefly0406.htm