With water carriers, spray droplets become smaller as they fall because of evaporation. For typical applications with ground applicators, droplets of 50 microns and less will completely evaporate to a residual core of pesticide before reaching the target. Droplets greater than 200 microns will have no significant reduction in size before deposition on the target. Evaporation of droplets between 50 and 200 microns is significantly affected by temperature, humidity and other weather conditions. Some pesticide formulations are more volatile than others. For example, 2,4 D or MCPA esters are susceptible to vapor drift, while 2,4-D or MCPA amines are practically non-volatile. Therefore, use formulations with low volatility to reduce vapor drift.