Efficacy of oil infused rice-based formulations of Beauveria bassiana (Balsamo) Vuillemi isolates (BPA/B7 and BKN-20) against Helopeltis theivora Waterhouse infesting tea

Abstract

The Beauveria bassiana, a soil-borne, filamentous fungus known for its entomopathogenic nature, and commonly used as a myco-insecticide to control pests. This white muscardine fungus produces a number of cyclodepsi peptides such as beauvericin which is considered for its insect toxicity. The insecticidal effectiveness of two native isolates of Beauveria bassiana (BPA/B7 and BKN-20) from tea ecosystem was evaluated against Helopeltis theivora, a major pest of tea plantations, and studied the potential of oil infused rice media to enhance fungal performance. These indigenous isolates were cultured on rice-based substrates supplemented with different organic oils, and the parameters like fungal growth, sporulation, spore viability, and pathogenicity were assessed under laboratory conditions besides its effect on tea mosquito bugs at varying concentrations. Results showed that, coconut oil-infused rice media produced the highest mycelia growth (3.78cm) and spore germination (86.1%). The isolate BPA/B7 grown on 1% coconut oil infused rice media caused over 80% mortality of H. theivora, outperforming commercial formulations. The findings indicated that, rice powder supplemented with 1% coconut oil is a cost effective and efficient substrate for large scale production of B. bassiana under laboratory condition.