Since 1996, glyphosate has been the predominant herbicide used postemergence for weed control in corn, soybean and cotton in the United States. Because of that, glyphosate-resistant weeds have become increasingly more prevalent in glyphosate-resistant crops which have forced many growers to use other herbicides. Herbicide programs that relied primarily on glyphosate for weed control often used rates as low as 5 gallon/acre (GPA). The other herbicides being used in row crops often require a higher carrier volume according to the label when compared to glyphosate which can be burdensome to the applicator, requiring the transport of more water, more refills and more potential of mixing errors. Additionally, there is growing concern about off-target movement of pesticides and what can be done to mitigate pesticide drift. Both drift and efficacy can be affected by spray quality and application decisions such as nozzle selection, operating pressure and components of the spray solution.
Applicators should be aware that pesticide applications are complex and there are many applicator driven decisions which will impact both the efficacy and off-target movement of pesticides following the application (Figure 1). Every applicator should be aware of the potential effects starting with properly mixing and agitating the spray solution through the resulting droplet size and deposition from atomization of the spray contingent upon nozzle selection, operating pressure and spray solution composition. In general, every applicator should be aware of the weather conditions (especially wind speed), boom height, droplet size and distance away from susceptible vegetation.