Lethal and Sub-Lethal Effects of Beauveria bassiana (Cordycipitaceae) Strain NI8 on Chrysoperla rufilabris (Neuroptera: Chrysopidae)

Abstract

A Mississippi Delta native strain (NI8 ARSEF8889) of Beauveria bassiana (Bals.-Criv.) Vuill. (Cordycipitaceae), isolated from Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), was tested on green lacewings, Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae) at 4 spray concentrations (7.02 × 104, 105, 106, and 107 spores per mL) to evaluate effects on reproductive rates and adult life expectancy of this insect predator. The application method simulated atomized spray, and concentrations tested were similar to those used to measure impacts of the fungus on L. lineolaris. Significant effects of B. bassiana on C. rufilabris adults were found, and the severity of impact depended on the concentrations tested. Beauveria bassiana impacted all demographic measurements of C. rufilabris reproduction and survival. Intrinsic and finite rates of increase and gross and net reproductive rates of adults treated with the highest concentrations tested were significantly decreased, whereas doubling time increased for adults treated with the lowest test concentrations. Based on these observations, C. rufilabris will be affected by sprays of B. bassiana targeted at L. lineolaris if adults are present at the time and location of treatment. The measured lethal concentration, LC50, of 2.11 viable spores per mm2 compares to an LC50 of 2.75 spores per mm2 determined previously for L. lineolaris. Higher concentrations of spores per mm2 were required for sporulation (SR50) of the entomopathogenic fungus on C. rufilabris (13.60 viable spores per mm2) than concentrations required for mortality (LC50).