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Case Study

Washoff of Pyrethroids from Building Material Surfaces

Urban applications of agrochemicals often include spraying the perimeter of buildings. When it rains, the chemicals on the walls and surrounding hard surfaces may wash off and be available for transport away form the treated area. However, little is known about how much washoff can occur.

To develop safe solutions, we conducted a study to examine the potential for washoff from applications of pyrethroids to different external building materials. The study simulated rain events using a laboratory research track sprayer and indoor rainfall simulator.

Our Findings

Cypermethrin formulated as Cynoff® EC Insecticide and Cynoff® WP Insecticide was applied at the maximum label rate to 10 different building material types. Three treated replicate rectangular slabs per type of building material and formulation were then subjected to a one-hour, one-inch-per-hour rainfall event.

Washoff from this study was quantified for both Cynoff® EC and Cynoff® WP Insecticides. Generally, more washoff occurred from smooth surfaces such as vinyl and aluminum and less from rough surfaces such as unpainted stucco. A manuscript is in preparation and, once accepted, can be made available upon request.


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