No. As long as the materials had an opportunity to dry, which takes about 30 minutes, it will stay adhered to the surface it was applied to. While rain, sun and wind will all break down pesticides, they are designed to withstand the elements for up to 90 days. On most days when there is a chance of rain, we will use a granulated material instead of liquid sprays. The granules work in a similar fashion to fertilizers in that they are time released by rain and moisture.