The effect of solar radiation on the survival of Entomophaga grylli (Entomophthorales: Entomophthoraceae) conidia

Abstract

Laboratory studies on the effects of simulated solar radiation on Entomophaga grylli conidial viability showed definite interactions between the duration and intensity of exposure to the light source. When either variable was increased, the viability of E. grylli conidia was reduced. An exponential decay model was developed based on combining these two factors into a single predictive variable, exposure to cummulative solar radiation in Langleys. A minimum of approximately 3 Langleys was required before conidial viability decreased, with nearly 100% noted after exposure to 20 Langleys. The exponential decay model when applied to conidial viability data collected in the field provided an excellent fit; however, parameter estimates were significantly different from laboratory estimates as conidia were found to survive different periods of time in different habitats. The model predicted over 95% mortality in the most open habitats after exposure to ca. 50 Langleys. As expected, conidia exposed in lower canopy areas and in canopies with more dense foliage survived significantly longer (ca. 95% mortality after exposure to 700 Langleys).