How should weather conditions influence application timing?

• A. Wind, temperature, and humidity affect drift and efficacy; postpone if conditions increase risk or reduce performance.
• B. Only rainfall determines whether to apply.
• C. Weather has no impact on pesticide efficacy.
• D. Apply only at night.

Answer: (A)

Weather controls how a spray behaves after you apply it. Wind speed and direction determine where droplets land, and if it’s too windy, drift increases and efficacy drops, so you should postpone. Temperature affects evaporation and volatility; very hot conditions can cause rapid evaporation or crop injury, while cool conditions can slow uptake. Humidity and leaf moisture influence how quickly droplets dry and deposit, with high humidity or dew changing coverage patterns. Rain or a forecast of rain within the label’s waiting period can wash away the product or reduce effectiveness, so wait for dry conditions and within the label’s timing. Night applications are not universally appropriate because inversions and poor coverage can increase drift and reduce deposition. In short, apply only when weather is favorable for good deposition and low drift, and always follow the product label.