Spray-dried encapsulated Beauveria bassiana formulations using biodegradable polymers

The conidia and mycelia of strain 139 of Beauveria bassiana (Balsamo Vuille min) wen formulated separately in gelatin, pectin and modified cornstarch b ases through a spray-drying process, yielding a fine dust. All formulations except the modified cornstarch base (100% recovery) lost weight after spra y-drying. We determined several parameters of each formulation such as yiel d, moisture content, stability at room temperature and at 4 degreesC, spore viability and mortality of Trichoplusia ni (Hubner) larvae in laboratory a nd greenhouse bioassays (using bean leaves). All of the formulations result ed in reductions in number and viability of encapsulated conidia (12% initi al viability) except the gelatin-based formulation that showed a 16% increa se in viability. Only the modified cornstarch conidia formulation had a sui table moisture content (less than or equal to4%). None of the formulations showed stability at room temperature after one month, while at 4 degreesC c onidia remained viable for up to 60 days. Conidial viability increased with time in the gelatin-based formulation. All formulations required an incuba tion period of 12 hours for conidia to begin germination, indicating damage suffered during the spray-drying process, Temperatures in laboratory and g reenhouse bioassays were 22-26 degreesC and the relative humidity was 80%. In larval mortality bioassays there was a significant difference in mortali ty induced by gelatin-based formulations, pure conidia suspensions and pure mycelia. Unformulated conidia. and mycelia exhibited high larval mortality .