What factors contribute to pesticide drift, and how can it be minimized?

• A. Wind speed, droplet size, nozzle type, and boom height; minimize with drift-reducing nozzles, coarse droplets, and applying in calm conditions
• B. Temperature, humidity, soil pH, and spray viscosity; minimize with wetting agents
• C. Sunlight, wind direction, soil moisture; minimize with shade cloth
• D. Crop height, time of day, leaf wax; minimize with dew point adjustments

Answer: (B)

Pesticide drift is about how droplets behave once they leave the nozzle. Environmental conditions that affect evaporation and air stability, like temperature and humidity, directly influence how large or how long droplets stay intact in the air. Hot, dry conditions tend to cause faster evaporation and produce smaller droplets that can be carried farther by wind, increasing drift risk. Spray viscosity, the thickness of the liquid, also matters because it shapes the droplet size during application—more viscous formulations typically form larger droplets that settle more quickly and are less prone to drift. Wetting agents, as adjuvants, help the droplets spread and adhere to the leaf surface, improving deposition on the target and reducing the amount that escapes to off-target areas. While soil pH can affect a chemical’s performance once it’s on the plant or in the soil, it doesn’t drive the physical drift behavior itself. So focusing on how temperature and humidity influence evaporation, how spray viscosity affects droplet formation, and using wetting agents to boost deposition provides a practical framework for minimizing drift.