Mists from sprays and volatilized herbicides on hot days can drift for miles in high winds and may damage nearby crops. Runoff from treated areas may kill algae, aquatic organisms, and fish. Careless flushing of equipment can contaminate soil, wells, and surface water, killing desirable plants and trees. Off-site applications can occur if boundaries are not clearly marked and known by the applicator. Because of potential environmental damage when using herbicides, the applicator must understand potential hazards and ways of avoiding problems.
Drift depends on the wind conditions.
For instance, if a gust of wind moves your swath 20 feet during a pass, you have an area that was skipped and an area that received a greater rate than required. You can avoid drift problems by knowing your product, your application equipment, and the degree that wind speed affects the herbicide's distribution. For instance, a granular formulation is less affected than a liquid spray. For your equipment, and the product you are using, develop wind speed guidelines that cause you to shut down. For liquid applications, that could be 5 mph.