Which of the following is a cause of vapor drift?

• A. Dissolving in water
• B. Low temperatures
• C. Nozzle pressure
• D. Volatilization

Answer: (D)

Vapor drift occurs when part of the pesticide evaporates into the air and is carried away by wind from the treated area. The direct mechanism behind this is volatilization—the pesticide changing from liquid to vapor and moving with air currents. This is more likely with products that have noticeable vapor pressure, especially under warmer conditions that promote evaporation, causing off-target movement. Dissolving in water keeps the chemical in liquid form, so it doesn’t become vapor. Low temperatures reduce evaporation, making vapor drift less likely. Nozzle pressure affects the size of spray droplets and liquid-phase drift, not the vapor phase.