BACILLUS THURINGIENSIS preparations proved to be highly effective for oakmoth control during field trials conducted in three areas of differing climate in northern California. The Bacillus thuringiensis preparations tested were Biotrol Dustable BTB 183 2.5D, Biotrol Wettable BTB 183 25 W, and Thuricide 90 TS 950-T. They were found to be equally effective for oakmoth control, though they differed in persistence of viable spores. Three types of equipment were used to apply the sprayable preparations, and all produced effective coverage but showed marked differences in wastage of material. Only one type of equipment was available for applying the dustable preparation. Application was timed to coincide with the early third instar of the oakmoth larvae, when a change in feeding behavior increased their exposure to the Bacillus thuringiensis. All three preparations were apparently fully compatible with the equipment for application, and no handling or disposal difficulties were encountered. The numbers of insect predators of oakmoth larvae were apparently unchanged by the Bacillus thuringiensis treatments and no phytotoxicity was noticed.

Mr. Hal Carter, Landscape Specialist, Monterey County, Mr. D. V. Cassidy, and Mr. Herman Schlapfer, all of the California State Division of Highways; Mr. Gary Pickering, Redwood Regional Park, East Bay Regional Park District; and Mr. Malcome Stebbins, on whose land much of the background work on oakmoths was carried out, assisted in these trials. The Bacillus thuringiensis preparations used for these trials were supplied by the manufacturers: Biotrol Dustable and Biotrol Wettable by Nutrilite Products Inc., Buena Park, California 90621, and Thuricide by International Minerals and Chemical Corp., Tempe, Arizona. This investigation was supported in part by Biomedical Sciences Support Grant FR-7006 from the General Research Support Branch, Division of Research Resources, Bureau of Health Professions Education and Manpower Training, National Institutes of Health.