What meteorological condition increases the likelihood of drift during pesticide applications?

The likelihood of drift during pesticide applications is significantly increased by temperature inversions. A temperature inversion occurs when a layer of warm air traps cooler air at the surface. This phenomenon can create stable atmospheric conditions that prevent the upward movement of air. As a result, any pesticide particles that are released during application can remain suspended in the lower atmosphere longer than they would under normal conditions. This stability allows them to drift away from the target area, carried by even light breezes, leading to unintended pesticide exposure to non-target areas or organisms.

In contrast, high humidity and low wind generally reduce the likelihood of drift since higher humidity can help the pesticide droplets to coalesce and fall to the ground more effectively, while low wind minimizes the force that would carry them away. Heavy rain typically washes away pesticides rather than facilitating their drift, and stable weather patterns might suggest consistent conditions, which would not inherently increase drift without the influence of temperature inversions. Understanding these factors aids applicators in making safe and effective decisions during pesticide use.