Spray dried microencapsulated formulation of Beauveria bassiana for control of Epilachna varivestis mulsant

Blastospores of Beauveria bassiana (Vuill) were produced in basal salts liquid medium supplemented with ammonium sulfate as the nitrogen source and with molasses as the carbon source. Whole cultures of B. bassiana containing 2.2×10⁹ blastospores/ml were used to produce a sprayable flour-basal microencapsulated formulation of B. bassiana (MFBb) at concentrations of 1, 3 and 5% of B. bassiana biomass (w/w) using a spray-drying process. The number of blastospores germinated/mm² on SDA agar microplate of these formulations after the drying process was determined. The number of blastospores germinated to each formulation shows statistical differences according to each B. bassiana concentration level (LSD, P <0.05). MFBb 1, 3 and 5% had 296 ± 2.59, 376 ± 2.35 and 444 ± 2.86, blastospores/mm², respectively. Eight days after the formulations were applied on first-instar larvae of the Mexican bean beetle reared in the laboratory using a dipping leaf bioassay, their toxicities were compared with an unformulated B. bassiana (UBb) and with the commercial bioinsecticide Mycotrol™. There were statistical differences of toxicity among treatments (Fc 94.089; p < 0.05). Mycotrol was highest with 96% larval mean mortality; UBb resulted in 77.3%, while MFBb 5, 3 and 1% yielded 72, 64 and 44%, respectively. MFBb 5% was the superior microencapsulated formulation; it's toxicity was statistically similar to that of UBb, and also demostrated acceptable toxicity compared to that of the commercial formulation.