Which factors increase vapor drift of pesticides?

The correct choice highlights that small droplets are more prone to vapor drift, particularly when they are produced under conditions of high pressure and high temperatures.

When pesticides are applied in the form of small droplets, they have a larger surface area relative to their volume. This increased surface area allows for more rapid evaporation, which can lead to volatilization—where the active ingredients become gaseous and drift away from the target area. High pressures can contribute to the formation of these small droplets, enhancing the potential for drift. Additionally, high temperatures can increase the rate of evaporation, further compounding the effects of small droplet size on drift.

In contrast, high pressures producing large droplets tend to have lower drift potential because larger droplets are less likely to evaporate quickly and are more likely to settle on the intended surface rather than drift away. High temperatures and relative humidity do not effectively explain an increase in vapor drift; while high temperatures can enhance evaporation, the relation with relative humidity is less direct. Low pressures and high humidity might contribute to different application challenges, but they do not inherently increase vapor drift the same way that small droplets do.