Virginia Commercial Pesticide Applicators CORE Exam

Which weather factor is NOT a contributing influence to pesticide drift?

1. Strong winds or gusts

2. Low humidity

3. High temperatures

4. Heavy rainfall

The correct answer is: Heavy rainfall

The correct choice indicates that heavy rainfall is not a contributing influence to pesticide drift. Drift typically occurs during the application of pesticides when they are airborne, and moisture from heavy rainfall would generally help settle those particles to the ground rather than carry them away. Rainfall has the effect of increasing the weight of droplets, which can reduce the likelihood of them being airborne once they hit the ground; this minimizes potential drift. On the other hand, strong winds or gusts, low humidity, and high temperatures can all significantly contribute to the phenomenon of pesticide drift. Wind can carry pesticide particles over long distances from the application site, while low humidity can cause pesticide droplets to evaporate quickly into vapor, allowing them to drift further. High temperatures can also accelerate evaporation and enhance the volatility of certain formulations, contributing to drift. These factors create conditions that increase the potential for pesticides to move beyond their intended target area, which is not the case with heavy rainfall.