Pesticide Overuse a Threat to California Agriculture

by Patricia McBroom

Farmers in California should reverse direction and reduce their reliance on pesticides or risk losing control over the growing numbers of chemically resistant insects while requiring ever stronger chemicals, according to a UC report.

Growers are trapped on a "pesticide treadmill." To combat resistance, they use ever-stronger chemicals, creating ever more resistant pests, says the report from the California Policy Seminar, a joint program of the university and state government that applies research to state concerns.

As a result of these practices worldwide, the number of resistant pests is growing exponentially, the authors point out. According to recent biological research, the number of insects and mites that have become resistant to chemicals since 1950 is up 10-fold, from less than 50 species to more than 450.

Written by researchers at the School of Public Health--Kathleen Walker, entomology graduate student; James Liebman, postdoctoral researcher; and William Pease, assistant adjunct professor of public health--this is the first policy analysis of the impact of pesticides on agricultural ecosystems in the state.

It warns that some species are becoming "superbugs," which evolve resistance to new pesticides very fast, so that each new chemical tends to work for a shorter period of time.

It also points out that the chemicals are killing beneficial species which have been keeping some pests under control, giving rise to the appearance of "secondary" pests.

As a solution, the report urges that the state take the lead in moving toward a mixed strategy of natural and chemical controls, thus reducing, but not eliminating, the use of pesticides.


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