Patterns of pesticide use in California and the implications for strategies for reduction of pesticides.

We used the California Pesticide Use Reports to study use of fungicides, bactericides, fumigants, and selected insecticides, primarily for vegetable, fruit, and nut production in California from 1993 to 2000. There were no obvious trends in decreased use of most compounds used to treat plant disease. However, growers have rapidly adopted recently introduced "conventional" compounds. There is very limited use of microbial biocontrol agents to control plant disease and no indication of an increase. We used case studies to explore the potential of different strategies to reduce pesticide use or risk. There have been reductions in use of organophosphate insecticides, largely by substitution with pyrethroids. Theoretically, replacement of "calendar spray" pesticide programs with "environmentally driven" programs could reduce pesticide use in years with lower disease pressure, but this assumes that the majority of growers currently use a "calendar spray" program and that growers who use less than recommended by an environmentally driven program would not increase their use.