Location: Fruit and Tree Nut ResearchTitle: Environmental Tolerance of Entomopathogenic Fungi: A New Strain of Cordyceps javanica Isolated from a Whitefly Epizootic Versus Commercial Fungal Strains
|WU, SHAOHUI - UNIVERSITY OF GEORGIA|
|TOEWS, MICHAEL - UNIVERSITY OF GEORGIA|
|Shapiro Ilan, David|
Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2020
Publication Date: 10/17/2020
Citation: Wu, S., Toews, M.D., Hofman, C.O., Behle, R.W., Simmons, A.M., Shapiro-Ilan, D.I. 2020. Environmental Tolerance of Entomopathogenic Fungi: A New Strain of Cordyceps javanica Isolated from a Whitefly Epizootic Versus Commercial Fungal Strains. Insects. 11(10). Article 711. https://doi.org/10.3390/insects11100711.
Interpretive Summary: In previous studies, we isolated and identified a new strain of insect-killing fungus that was collected from whiteflies in cotton fields of Southern Georgia, USA. The objective of this study was to test the level of tolerance of this new strain to environmental conditions as compared to commercial fungal strains that are used in natural insect control. We exposed the new strain and three commercially available strains of biopesticides (BotaniGard®, Met52® and PFR-97®) to different temperatures and strong UV radiation before examining post-treatment viability and virulence (killing power) against a common model organism for insect pathology, the greater wax moth larvae. We found that the new strain has similar levels of activity to commercial strains at moderate temperatures, but higher tolerance than PFR-97® to extremely low and high temperatures and strong UV intensity. These findings suggest that the new fungal strain has potential for commercial development as an alternative to PFR-97® for managing certain types of insect pests.
Technical Abstract: A new strain of Isaria javanica (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 UV light was compared among this strain and three commercial strains of entomopathogenic fungi (Metarhizium brunnuem F52, Isaria fumosorosea Apopka97, and Beauveria bassiana GHA). Under 10-30°C, I. javanica wf GA17 responded similarly to the other fungi, with the highest virulence against Galleria mellonella at 25°C, followed by 20, 30 and 15°C; the lowest virulence was observed at 10°C. At 35 and 40°C, I. javanica wf GA17 had lower tolerance than M. brunnuem F52 and B. bassiana GHA, but was superior to I. fumosorosea Apopka97 in conidia viability and post-treatment virulence. After exposure to -20°C for 56 d, I. javanica wf GA17 exhibited lower germination than M. brunnuem F52 and lower virulence than M. brunnuem F52 and B. bassiana GHA, but higher germination and virulence than I. fumosorosea Apopka97. Following exposure to strong UV light, viability and virulence of all fungi were reduced with increasing exposure periods. Increased environmental tolerance of I. javanica wf GA17 over I. fumosorosea Apopka97 suggests that the new strain could have applicability for commercial pest management.