What factors influence drift and volatilization of pesticides after application?

• A. Only humidity
• B. Only wind speed
• C. Droplet size, nozzle type, spray pressure, wind speed and direction, temperature, humidity, and atmospheric inversions.
• D. Only temperature

Answer: (C)

Drift and volatilization depend on both how the spray forms droplets and the conditions around them after application. The size of the droplets is key: finer droplets stay suspended longer and can be carried farther by air currents, while larger droplets tend to deposit closer to the application site. That’s why nozzle type and spray pressure matter—they control the droplet size distribution. If you use a nozzle that creates many small droplets or crank up the pressure, drift risk goes up.

Wind speed and direction are the transport factors: stronger winds push droplets farther and in directions you might not expect. Temperature affects evaporation and volatility—warmer air makes active ingredients evaporate more quickly and can increase the amount of pesticide that becomes vapor in the air, which contributes to volatilization. Humidity also influences evaporation rates and droplet behavior; in drier air, droplets can shrink faster and become more prone to drift and premature volatilization.

Atmospheric inversions add another layer of risk by trapping air close to the ground and limiting vertical mixing. Under an inversion, pesticides released near the surface can linger and move along the ground or stay concentrated in a shallow layer, enhancing both drift and volatilization.

Because all these factors interact, the overall risk of drift and volatilization is governed by many conditions at once, not just a single factor.