Effect of Two Strains of Beauveria bassiana on the Fecundity of Nezara viridula L. (Heteroptera: Pentatomidae)

Abstract

The southern green stink bug (SGSB) Nezara viridula (L.) (Heteroptera: Pentatomidae), has become a significant pest of soybean and cotton in southern Central America and in the lower mid-southern U.S. A laboratory colony of SGSB was used to evaluate the effect of two isolates of Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) including the commercial strain GHA and the Mississippi Delta native NI8 strain on the fecundity of this pest. Water control, Tween-80, and four concentrations of each strain (n × 104, 105, 106, and 107) were evaluated. Both native and commercial isolates with the highest concentrations were susceptible to the SGSB. Females, however, were much more pathogenic to both strains than males. Lethal concentration of the native strain (236 spores/mm2) was 1.4-fold lower (326 spores/mm2) than the GHA strain for females evaluated 20 d post-exposure. Greater concentrations (1.1 × 107 spores/mm2, 5.2 × 106 spores/mm2) were required to kill males with both strains native and commercial, respectively. For controls and lower concentrations, cumulative fecundity ranged from 1178 to 2082 eggs/10 couples/life reproduction, compared with 597 and 673 eggs/10 couples sprayed (n × 106 and 107) with the native NI8, respectively, and 386 eggs/10 couples sprayed (n × 107) with the commercial GHA.