Improved Rainfastness and UV Resistance of Microbial Pesticides

Bacillus thuringiensis (Bt) is one of the most widely used microbial pesticides and currently represents the largest share of the biopesticide market (~67%). Bt is highly active against insects such as caterpillars, mosquito larvae, and blackflies that transfer river blindness in Africa. During the sporulation of Bt, crystal aggregates of proteins are produced, which along with its spores, are responsible for its high insecticidal activity. However, Bt lacks long-term activity in the field due to the UV sensitivity of the spores and lack of persistence of crystal proteins on plant leaves due to rain. In this study, we present the development of materials providing rainfastness and UV resistance that perform above benchmarks for both the liquid and dry flowable Bt formulations currently available. The high rainfastness observed was maintained after spray drying of liquid Bt formulations containing our rainfastness agents and redispersion in water of the dry products obtained. Finally, we present the performance of different OMRI-certified rainfastness agents.