Studies dealing with shelf life of entomopathogenic fungi have focused primarily on cold or moderate ambient temperatures (Walstad et al., 1970; Aregger, 1992; Silva, 2006). Also, most stud- ies have involved ‘‘open’’ storage, in which air exchange takes place between the external and internal atmosphere of packages (non hermetic containers). Variable results have been reported in open storage studies of Beauveria bassiana (Bb) conidia at high ambient temperatures (P30 °C). Marques and Alves (1996) reported that viability of conidia with 15.5% moisture content (MC) stored at 30 °C was greatly reduced within 30 days, while conidia formu- lated in sunflower oil retained 80% viability for 90 d but only ca. 30% viability for 120 d. Time for initial viability to drop to 80% was less than one week at 37 °C for a powder with unspecified moisture content (Jin et al., 1999). Significant reduction in viability of formulated aerial conidia with unspecified moisture content occurred 2–3 months after storage at 30 °C (Kassa, 2003).