A still‐air, controlled experiment showed that the use of spherical targets resulted in a slight underestimate (7%) of the deposition of spray droplets (mean diameter ≈ 180μ). This error was attributed to interception by the wire supports suspending the spheres. Comparison of sphere and flat card catch data from a USDA APHIS open field, aerial spray trial demonstrates that the impaction on the cards decreases as the wind speed increases and that they are generally unsuitable for pesticide accountancy. The spheres only have small errors when used to sample mass flux of pesticide spray.