Title: Storage conditions affect speed of germination in Beauveria bassiana and Metarhizium anisopliae conidia Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 24, 2009
Publication Date: August 16, 2009
Citation: Faria, M., Ramos, M., Hajek, A.E., Wraight, S.P. 2009. Storage conditions affect speed of germination in Beauveria bassiana and Metarhizium anisopliae conidia. Meeting Abstract. 42:75. Technical Abstract: The retention of high viability during storage is essential for effectiveness and thus market acceptance of fungus-based biopesticides. The length of adequate shelf-lives for mycoinsecticides is controversial, with proposed requirements varying from a few weeks to 18 months. Shelf-life determinations under non-refrigerated conditions, especially high temperature regimes common in tropical regions (30-50 degrees Celsius), deserve growing attention. Most previous studies dealing with high ambient temperatures have involved storage environments where important parameters such as temperature and water activity were uncontrolled. To our knowledge, the longest reported survival (retention of greater than 80 percent viability) of Beauveria bassiana under tropical conditions was 80 days at 40 degrees Celsius and 17 days at 50 degrees Celsius (Hong et al., 2001; Mycol. Res. 105, 597-602). In this study, we investigated effects of modified storage atmospheres on longevity of B. bassiana GHA conidia. Increasing oxygen decreased survival. Conidia with 0.10 water activity stored at 50 degrees Celsius for 33 days in 0.3, 2.5, 4.8, 12.3 and 22.4 percent oxygen (balanced with nitrogen) showed 69, 64, 55, 27, and 16 percent viability, respectively. Replacement of oxygen with carbon dioxide, nitrogen, helium, or hydrogen produced similar increases in longevity. Dry conidia stored at 40 degrees Celsius in a carbon dioxide/nitrogen atmosphere retained 89 percent viability for 3 months; viability dropped to 48 percent after 180 days. Viability of conidial powders stored in the absence of oxygen for 33 days at 50 degrees Celsius was significantly increased (from ca. 50 to 80 percent) by reducing water activity from 0.14 to 0.10. Air leakage into our storage containers (glass jars) was detected after a few months of storage, and we believe that use of truly hermetic packaging could substantially improve these results.