Pyrethroid insecticides have been under scrutiny for several years resulting in recent changes to water quality requirements. The changes set monitoring levels for pyrethroids at nanograms in surface waters. Consistent exceedances of the levels could result in additional restrictions to pyrethroid use, or designate a drain as impaired with future restoration to correct the water quality. Last year, one of the water quality coalitions had a detection that could be problematic under the new standards.

What does this mean to growers and applicators in rice country?

Our industry does a great job applying pyrethroids for early season pest control. Most applications are boarder treatments to target the area of the field insect pests thrive. We need to be aware of all field boundaries when making boarder treatments. Fields next to a drain can have the application adjusted to cover more of the field rather than the edge of the boarder.

What is a TMDL?

Total Maximum Daily Load is a regulatory term from the U.S. Clean Water Act. The TMDL defines a plan for restoring impaired waters by identifying the maximum amount of “pollutant” the water body receives while still meeting water quality standards.

What are 303(d) listed water bodies?

Under the U.S. Clean Water Act, this is the list of impaired or threatened waters (streams, rivers, segments, lakes, etc.) that identify a pollutant as causing the impairment. The list is updated every two year. The pyrethroid TMDL lists 14 waterbodies: nine from municipal storm water and five from agricultural discharge in the Central Valley.

List of pyrethroid insecticides

Pyrethroid is the class of insecticide that includes the active ingredients: Bifenthrin, Cyfluthrin, Cypermethrin, Esfenvalerate, Lambda-cyhalothrin and Permethrin. The regulation is per active ingredient with no relation to the labeled name.

Click here to download the Pyrethroid Fact Sheet