Which of the following conditions contribute most to pesticide spray drift?

Pesticide spray drift is significantly influenced by factors related to droplet size and delivery method. The combination of a small orifice and high pressure during application creates very fine droplets. These small droplets are more susceptible to environmental factors such as wind and thermal currents, which can carry them away from the intended area, resulting in drift. When droplets are generated under high pressure through small nozzles, even slight wind can move these ultra-fine particles farther than larger droplets, which tend to settle to the ground more quickly.

Other factors can affect drift, but they do not enhance the potential for drift as significantly as the conditions described in this answer. High temperatures and low humidity can contribute to quicker evaporation and may influence how droplets behave, but they do not inherently create conditions that lead to finer droplet formation like small orifice size and high pressure do. Additionally, larger droplet sizes generally reduce drift potential as the droplets tend to fall to the ground closer to the application site, and calm winds would actually minimize drift rather than promote it.