Technical Abstract: Optimization of shelf life is critically important for biocontrol products containing living microorganisms. Spores of Colletotrichum truncatum, a fungal pathogen of the weed, hemp sesbania, were formulated in wheat flour-kaolin granules ("Pesta"). Granules were conditioned at water activities of 0.04, 0.13, 0.35, 0.51, and 0.74 during storage at 25 C over desiccant or saturated salt solutions. The best shelf life resulted with samples at a water activity of 0.13 (13% relative humidity), and this gave 87% viability after one year. Shelf-stable and effective biocontrol products will offer an alternative to chemical pesticides in some agricultural applications. Pesta that contains safe, biodegradable, agricultural commodity ingredients is a promising addition to biocontrol agent formulation technology.