Volume 8 Issue 11
WSDA, Natural Resources Assessment Section Surface Water Pesticide Monitoring Program
October 30, 2019
The Washington State Department of Agriculture (WSDA) began monitoring pesticides in Bertrand Creek starting in March, 2018. The two sampling sites are at the H Street Road (Upper Bertrand Creek) and Rathbone Road (Lower Bertrand Creek) bridges. This is the seventh consecutive year WSDA has monitored Bertrand Creek as part of a larger study testing for pesticides in salmon-bearing streams statewide during typical pesticide use periods (March – October).
In 2018, WSDA monitored Bertrand Creek from March – September for a total of 26 visits and tested for 144 different pesticide compounds. At Upper Bertrand Creek, WSDA detected 45 different compounds, with 450 total detections. The compounds detected at least 50% of the visits were:
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Of the 450 total detections, 30 were higher than WSDA’s assessment criteria. WSDA’s assessment criteria are related to state and federal water quality criteria. When a detection exceeds WSDA’s assessment criteria, it is approaching levels that may result in harm to aquatic life. The five compounds exceeding these criteria were imidacloprid (accounting for 26 of the 30 elevated detections), 4,4’-DDD, 4,4’DDE (both DDT breakdown products), bifenthrin (a pyrethroid insecticide with a variety of labeled uses) and diazinon (an organophosphate insecticide).
At Lower Bertrand Creek, WSDA detected 60 different compounds, with 643 total detections. The compounds detected 50% or more of the time were:
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Of the 643 total detections, 30 exceeded WSDA’s assessment criteria. The compounds exceeding these criteria are: 4,4’-DDD, 4,4’-DDE, bifenthrin, diazinon, imidacloprid (accounting for 18 of the 30 exceedances), malathion (an organophosphate insecticide) and pentachlorophenol (a wood preservative).
In 2019, WSDA tested for 147 pesticide compounds including insecticides (neonicotinoids, pyrethroids, organochlorines, organophosphates, carbamates, and others), herbicides, fungicides, wood preservatives, historically-used pesticides, and breakdown products. Results of 2019 pesticide monitoring will be available in 2020. In addition, WSDA monitors total suspended solids, stream flow, pH, dissolved oxygen, conductivity, and continuous air and water temperature at all site visits. WSDA, the Environmental Protection Agency, and the National Marine Fisheries Service use this data to improve exposure assessments for pesticides registered for use in Washington. Visit WSDA’s website for more information and reports from other areas: https://agr.wa.gov/AgScience.
Preventing contamination of surface water is critical for protecting aquatic systems and fish. Using pesticides according to their label instructions and paying attention to environmental hazard and precautionary label statements helps protect fish and the environment. Carefully plan pesticide applications and take into account the presence of backyard drains, impervious surfaces, sprinkler timing, and any potential for drift and runoff.