By Bob Johnson, Ag Alert
California Department of Pesticide Regulation scientists say they are shifting their water-quality efforts toward preventing problems rather than to focus on cleaning up materials after they have reached rivers, streams or lakes.
In the Central Coast Region, DPR regulators monitor six rivers, creeks and sloughs in the Salinas Valley and an additional four creeks in the Santa Maria Valley for insecticides that can be detected at trace levels, measured in parts per billion.
“We mainly concentrate on insecticides, because they may also kill aquatic insects,” said Anson Main, DPR senior environmental scientist.
Main discussed recent findings of the surface water monitoring program with the farmers and pest control advisors who tuned into a December online pest management seminar offered by University of California Cooperative Extension.
“The U.S. Environmental Protection Agency establishes a threshold above which the material could be problematic,” Main said. “You can have materials that are frequently detected but are rarely above the benchmark level—but some of the benchmarks are being revised to be stricter.”
The benchmark for acute concentrations of the neonicotinoid imidacloprid is 385 nanograms per liter, but for chronic concentrations just 10 nanograms, and for the pyrethroid bifenthrin 80 nanograms per liter for acute concentrations, and just 1.3 nanograms for chronic concentrations.
Main said those two materials were most likely to be found above benchmark levels in Salinas Valley surface-water tests conducted during the last five years, while in the Santa Maria Valley, imidacloprid and malathion were most likely to be found above benchmark levels.
Malathion is most widely used as an attempt to control lygus bugs in strawberries, Main said, and there has been a trend toward the development of resistance.
Imidacloprid is detected in virtually every sample taken in Central Coast surface water, although frequently at harmless levels, he said.
Pyrethroids are more commonly found in the water in the Salinas Valley than the Santa Maria Valley, Main said, and the main challenge is the ability of these materials to adhere to sediment that eventually reaches creeks and rivers.
Detections in Central Coast surface waters of chlorpyrifos, the active ingredient in Lorsban, plummeted during the last decade, he said, as state regulators moved toward eliminating use of the material.
Because integrated pest management programs and structural mitigations are important parts of the effort to keep materials out of the water, especially at benchmark levels, Main said DPR also cooperates in studies of techniques for keeping potential materials out of surface water. Those methods include vegetated strips in the Salinas area or a bioreactor at California State University, Monterey Bay.
Because it is easier to keep potentially harmful materials out of rivers and creeks than remove them once a problem has developed, Main said, regulatory scientists are emphasizing studies that highlight potential surface water issues during the registration process.
“Prevention is something we’re paying a lot more attention to when we consider registration of a new product,” he said. “Our goal is to make prevention a more significant component of the program.”
