The influence of solar radiation, substrate, temperature, humidity, and chemicals on the stability of entomopathogenic bacteria of the genus Bacillus is reviewed. Solar radiation appears to be the key survival factor affecting Bacillus thuringiensis spores deposited on foliage. This is modulated by rainfall and the plant species serving as substrate. Where solar radiation has a minimal influence: i.e., in beehives, stored products and soil, Bacillus appears to be more stable. Both low temperature and low relative humidity enhance stability. Among leaf extracts tested, those from conifers are more inhibitory than those from deciduous plants. Carbaryl, chlordimeform, boric acid and chitinase enhance pathogenicity while propoxur increases spore survival.