Which two factors should applicators be most aware of to avoid vapor drift?

• A. Nozzle size and droplet spectrum.
• B. Application rate and environmental temperature.
• C. Temperature and pesticide volatility.
• D. Wind speed and humidity.

Answer: (C)

Vapor drift happens when enough of the pesticide evaporates into vapor and travels with air currents to off-target areas. The two factors that most influence this are how hot it is and how volatile the chemical is. Higher temperatures push more of a volatile product into the gas phase, increasing the amount of vapor that can drift away from the treated area. Pesticide volatility is a property of the chemical (and formulation): products with high volatility readily become vapors even at typical application temperatures. So, warmer conditions combined with a highly volatile product pose the greatest potential for vapor drift.

While other factors like the way droplets form or ambient wind can affect drift, they pertain more to spray droplets than to vapor drift. Understanding temperature and volatility helps you assess and mitigate vapor drift risk by timing applications for cooler periods and selecting lower-volatility formulations when possible.