Spray-dried encapsulated Beauveria bassiana formulations using biodegradable polymers

The conidia and mycelia of strain 139 of Beauveria bassiana (Balsamo Vuillemin) were formulated separately in gelatin, pectin and modified cornstarch bases through a spray-drying process, yielding a fine dust. All formulations except the modified cornstarch (100% recovey) lost weight alter spray-dryins. We determined several parameters of each formulation such as yield, moisture content, stabitlity at room temperature and at 4°C, spore viability and mortality of Trichoplusia ni (Hübner) larvae in laboratory and greenhouse bioassays (using bean leaves). All of the formulations resulted in reductions in number and viability of encapsulated conidia (12% initial viability) except the gelatin-based formulation that showed a 16% increase in viability. Only the modified cornstarch conidia formulation had a suitable moisture content (≤4%). None of the formulations showed stability at room temperature after one month, while at 4°C conidia remained viable for up to 60 days. Conidial viability increased with time in the gelatin-based formulation. All formulations required an incubation period of 12 hours for conidia to begin germination, indicating damage suffered durring the spray-dryig process. Temperatures in laboratory and greenhouse bioassays were 22-26°C and the relative humidity was 80%. In larval mortality bioassays there was a significant difference in mortality induced by gelatin-based formulations, pure conidia suspensions and pure mycelia. Unformulated conidia and mycelia exhibited high larval mortality.