| Summary: | A new strain of <i>Cordyceps javanica</i> (wf GA17) was observed causing widespread epizootics among whiteflies in Southern Georgia in 2017. The tolerance of conidia to environmental factors including variable temperature and ultraviolet (UV) light was compared between this strain and three commercial strains of entomopathogenic fungi (<i>Metarhizium brunneum</i> F52, <i>Cordyceps fumosorosea</i> Apopka97, and <i>Beauveria bassiana</i> GHA). Under 10–30 °C, <i>C. javanica</i> wf GA17 responded similarly to other fungi, with the highest virulence against <i>Galleria mellonella</i> at 25 °C, followed by 20, 30, and 15 °C; lowest virulence was observed at 10 °C. At 35 °C and 40 °C, <i>C. javanica</i> wf GA17 had lower tolerance than <i>M. brunneum</i> F52 and <i>B. bassiana</i> GHA, but was superior to <i>C. fumosorosea</i> Apopka97 in conidia viability and post-treatment virulence. After exposure to −20 °C for 56 d, <i>C. javanica</i> wf GA17 exhibited lower germination than <i>M. brunneum</i> F52 and lower virulence than <i>M. brunneum</i> F52 and <i>B. bassiana</i> GHA, but higher germination and virulence than <i>C. fumosorosea</i> Apopka97. Following exposure to strong UV light, viability and virulence of all fungi were reduced with increasing exposure periods. Increased environmental tolerance of <i>C. javanica</i> wf GA17 over <i>C. fumosorosea</i> Apopka97 suggests that the new strain could have applicability for commercial pest management.
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