Spring is underway, and across California, gardeners and farmers are combating the season’s annual pest problem: insects. But the pesticides that protect our roses and our lettuce may be harming more than just the bugs. Pesticides, in particular pyrethroids, are making their way from our gardens, farms, and houses into our watersheds, where they pose a serious threat to California’s aquatic populations. With annual pesticide use expected to peak in the coming months, now is the time to ask some questions. What are pyrethroids? How are they impacting our water systems? What is being done to mitigate the potential problems associated with their use?

Since the late 19th century, pyrethroids have been around and are similar to some naturally occurring insecticides, called pyrethrins, found in chrysanthemum flowers. But unlike pyrethrins, pyrethroids are manufactured chemicals designed to quickly incapacitate insect nervous systems and simultaneously resist environmental degradation. Their low toxicity to humans, mammals, and birds makes them ideal for a variety of agricultural, public health, and domestic purposes. Pyrethroid compounds are effective insecticides employed on farms and in homes across the US. In particular, pyrethroids are an efficient…