Microgen® application ofBacillus thuringiensis(Bt) formulations on pear compared favorably to the conventional high volume application by handgun but was dependent upon calm weather conditions for effective coverage. The viable half life of Bt spores on pear fruit was related to their placement on the fruit surface. Spores located in protected areas at the base of the fruit remained viable for a longer period (half life = 1.3–2.5 days) than did spores exposed to sunlight on the perimeter of the fruit (half life = 1.2–1.4 days).Early season control of fruit tree leafroller (Archips argyrospilusWalker) (Lepidoptera: Tortricidae) on pear using Bt formulations was attempted using both the Microgen and handgun. Both application methods had a suppressive effect on the number of rolled leaves and early fruit damage compared to the control. The amount of damaged fruit between treatments at harvest was not significantly different.