How do temperature and humidity affect pesticide performance and drift?

• A. Temperature affects volatilization and degradation; humidity influences deposition and drift; extreme heat can increase volatilization; wind and humidity interplay.
• B. Only humidity affects pesticide performance.
• C. Temperature and humidity have no effect.
• D. Only wind matters for drift.

Answer: (A)

Environmental conditions determine how well a pesticide performs and how far it can drift by affecting both what stays where it’s applied and what escapes into the air. Temperature plays a big role: higher temperatures increase volatilization, so more of the active ingredient can evaporate before it hits the target, and many pesticides degrade faster in heat, which can shorten how long they remain effective. Extreme heat can amplify these losses, reducing performance.

Humidity influences how droplets behave after application. Higher humidity tends to slow evaporation, helping droplets stay larger and deposit more on surfaces, which improves deposition and often reduces drift. Low humidity speeds evaporation, creating finer droplets that can stay airborne longer and travel farther with the wind. Since wind drives drift, humidity’s effect on evaporation interacts with wind to determine how far droplets move. In short, temperature mainly affects volatilization and degradation; humidity mainly affects deposition and drift, with their interplay shaping the overall outcome.