Long-term storage stability of Beauveria bassiana ERL836 granules as fungal biopesticide

Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) ERL836 has been commercialized under the name ChongchaeSak to control an agricultural insect pest, the western flower thrips Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), in the Republic of Korea. As soon as it was launched in 2017, it became a popular product and has received a positive response. However, study of the storage stability of the fungus ERL836 has yet to be investigated. To determine the optimum conditions for long-term storage, we assessed conidial viability and insecticidal activity of B. bassiana ERL836 according to storage temperature and culture substrate. Viability of B. bassiana ERL836 conidia from mycotized grains (millet and rice) stored at low (4 °C) and moderate (25 and 30 °C) temperatures was maintained at >85% for 24 and 18 months, respectively, along with insecticidal activity. In contrast, the samples stored at 37 °C showed low germination rate (about 80% germination rate for only 5 months). This result suggests that low and moderate temperatures (4 to 30 °C) conserve B. bassiana ERL836 viability and virulence.