Which weather conditions should influence pesticide application decisions?

• A. Wind speed/direction, temperature, humidity, rainfall forecast; avoid spraying in high wind or when inversion exists; delay if rain is imminent.
• B. High humidity.
• C. Temperature above 90 F only.
• D. Wind speed only.

Answer: (A)

Weather conditions determine how droplets behave after you spray—drift, deposition, evaporation, and wash-off all hinge on them. The best guidance you can follow includes wind speed and direction to keep droplets from moving off target, and to place them where intended; temperature affects how quickly a product evaporates or degrades and can change whether droplets stay in the target area or become airborne. Humidity matters because it influences droplet evaporation and deposition, and rainfall forecasts are crucial because rain can wash off product, reduce efficacy, and increase environmental risk. Inversions and high wind are especially problematic for drift, so spraying is delayed when those conditions exist. Other single-factor choices miss these linked effects and don’t fully protect against off-target movement or wash-off.