Effects of host plant characteristics on spray deposition

Previous studies have shown that the effect of Bacillus thuringiensis var. kurstaki (Btk) on painted apple moth (PAM; Teia anartoides Walker) efficacy varies significantly depending on the host plant species. This study tested the hypothesis that host plant architecture influenced deposition of aerially applied Btk and its consequent efficacy against PAM. Laboratory experiments demonstrated that the architecture of six host plants had a significant influence on Btk dose per unit leaf area and dose per unit leaf weight. However, the large host plant effect on PAM mortality from Btk could not be explained in terms of variation in the amount of spray intercepted.