RELATIONSHIP BETWEEN MICROBIAL NUMBERS AND DROPLET SIZE IN AERIAL SPRAY APPLICATIONS

Abstract

AbstractExperiments were designed to determine the actual number of spores and crystals of Bacillus thuringiensis (B.t.) and of nuclear polyhedral virus and entomopoxvirus deposited at ground level per unit area and to determine any change in spore:crystal ration following aerial application in forested plots.The results indicate that: (1) The estimation of B.t. aerial spray deposits by the commonly used agar plate method grossly underestimates the deposit rates of active ingredient. The tracer dye method more accurately estimates deposit rates for both B.t. and entomopathogenic viruses. As a dye 0.1% Erio Acid Red XB is recommended. (2) The relationship between drop size and the number of spores and crystals or virus inclusion bodies/drop is curvilinear. This relationship probably holds true regardless of spray volume rate. All visible spray deposits at ground level contained some active ingredient. (3) With B.t. sprays the sporexrystal ratio emitted from the aircraft is not changed upon target impact.