Why is it important to document weather conditions at the time of pesticide application?

• A. Weather affects drift potential, volatilization, and efficacy; record wind, temperature, humidity, and precipitation.
• B. Weather has no impact on pesticide performance.
• C. Only wind matters; others ignored.
• D. Documentation is optional.

Answer: (A)

Weather conditions at the time of application influence drift, volatilization, and how effectively the pesticide works. Wind speed and direction determine how far and where droplets move beyond the target, so documenting wind helps you assess drift risk and meet label requirements. Temperature and humidity affect how quickly droplets evaporate and how the product behaves on plant surfaces, which in turn impacts deposition, uptake, and potential losses through volatilization. Precipitation or recent rainfall, as well as humidity levels, can alter wash-off and absorption, changing efficacy and environmental impact. Recording wind, temperature, humidity, and precipitation provides a complete picture of the conditions that affected the application, supports label compliance and proper interpretation of results, and aids in planning future applications. Other options ignore how these factors together influence performance and drift, making them incomplete.