Performance of Beauveria bassiana (Balsamo) Vuillemin Stored as Oil Cultures under Different Temperature Regimes

Entomopathogenic Fungal agents play an important role in controlling pest population. Besides isolating and exploiting the virulent fungal agents it is essential to maintain its viability for longer period at affordable cost, thereby they could be employed for further research. Usage of oils and storage at lower temperatures prevent conidial desiccations and could be comparatively a cheaper alternative to freeze drying and cryopreservation to maintain its virulence for extended periods. Oil cultures of Beauveria bassiana (Balsamo) Vuillemin were prepared from the laboratory-maintained isolate by using two vegetable oils viz., Rice Bran oil, Sesamum oil and two mineral oils viz., Liquid Paraffin oil and Heavy grade Mineral Oil. Prepared oil cultures were stored under three different temperature regimes viz., at room temperature (28 ± 3ºC), refrigerated condition (4ºC) and freezing temperature (-20ºC). These 12 cultures stored at different temperatures along with crude culture and untreated control were evaluated for viability and virulence against third instar Spodoptera litura (Fabricius) larvae on the day of preparation (0 DAS) and upto 180 days under laboratory conditions. Among all oil cultures, Sesamum oil cultures and Liquid Paraffin oil cultures stored at -20ºC performed well with highest conidial germination of 87.85% and 83.57% and highest larval mortality of 90.00% and 86.67% on the day of preparation (0 DAS). After 180 DAS of storage, conidial germination in these two formulations was in the range of 62.87% to 61.43% and larval mortality was 60.00%. Comparatively, least performance was observed in mineral oil formulations stored at room temperature(T1) and in unformulated crude cultures.