Submitted to: Society of Invertebrate Pathology
Publication Type: Abstract Only
Publication Acceptance Date: 7/21/1995
Publication Date: N/A
Technical Abstract: Environmental conditions such as rainfall and sunlight can limit the effectiveness of biopesticides. Using the bacterium Bacillus thuringiensis as a model, we have developed a variety of adjuvant materials based on surplus farm commodities. This paper will report on the use of flour/sucrose, gluten, and casein in side-by-side comparisons for activity as solar screens and as protectants against rainfall. The test was conducted on cabbage, and Trichoplusia ni was used as a test insect to measure residual activity of B. thuringiensis on leaf disks collected from the field. Rainfall and sunlight both significantly affected activity. Treatments receiving approximately 3.2 cm rain in a 3-hour period lost approximately 20% of the original activity across all treatments. Significant treatment by rain interactions demonstrated that not all treatments responded similarly to the rain, however. In fact, no significant differences in mortality were observed between leaves receiving rain and those not receiving rain when treated with formulations containing casein or gluten. Dipel 2X and flour-sucrose treatments both significantly lost activity. Linear regression demonstrated half lives of 7.1, 5.7, 4.8, and 4.3 days for treatments containing gluten, casein, flour-sucrose, and Dipel 2X, respectively. These data indicate that rain and sunlight significantly affect residual activity of B. thuringiensis and that formulation or adjuvant ingredients may mitigate against these forces.