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Educating Pesticide Applicators for Surface Water Quality Protection, Whatcom County

Volume 6 Issue 3

WSDA, Natural Resources Assessment Section
Surface Water Pesticide Monitoring Program

The Washington State Department of Agriculture (WSDA) has been conducting monitoring of pesticides in surface waters of Whatcom County.  Most pesticides detected are found at very low concentrations and are not of concern.  Preventing additional contamination is important for agriculture and maintaining pesticide product use.  Certain pesticides have been detected in recent years at concentrations that are approaching an aquatic benchmark or level of concern.  These detections are considered Pesticides of Concern (POC).  A surface water POC is a detection that is greater than 50% of an aquatic benchmark.  Protecting aquatic systems and fish is very important while maintaining the proper use of crop protection pesticides.

The pesticides found in surface water monitoring of small wadable streams, such as Bertrand Creek, the last several years are numerous.  Bertrand Creek was sampled at two locations once per week for a total of 24 times between March and September, 2016.  The fungicides detected include boscalid, chlorothalonil, cyprodimil, fludioxonil, metalaxyl, myclobutanil, propiconazole, and pyradostrobin.  The herbicides detected include 2,4-D, dicamba, dichlobenil, diuron, isoxaben, MCPA, mecoprop, metolachlor, oxadiazon, simazine, terbacil, and triclopyr acid.  The insecticides detected include oxamyl, imidacloprid, malathion, and thiomethoxam.  The majority of the pesticides detected showed very low part per billion (ppb) concentrations and are not an immediate concern for aquatic life, but will continue to be monitored.  Most of the detections occur in the spring and early summer months during the peak application periods.  The pesticides found ten or more times in 2016 were boscalid, bromacil, chloranthraniliprole, dichlobenil, diuron, imidicloprid, metalaxl, oxamyl, simazine, sulfrentrazone, and thiamethoxam.  Two pesticides were found at a higher concentrations where they are considered to be a POC, the herbicide simazine and the insecticide malathion.  Bifenthrin, which was found at a high concentration during 2015, was not detected in 2016.

We encourage applicators to completely assess their uses of the pesticides that have been detected in surface water.  Preventing contamination to surface water is very important for the protection of aquatic systems and also maintaining proper crop protection.  Plan applications carefully, and follow the label directions listed for the environmental hazard and precautionary label statements.  Pay extra attention to label statements, weather factors, and vulnerabilities of the application site when applying pesticides, especially when using a pesticide product that is detected often or one that is a POC like malathion.