Nezara viridula (Hemiptera: Pentatomidae) Cuticle as a Barrier for Beauveria bassiana and Paecilomyces sp. Infection

The objective of this study was to evaluate the ability of two Beauveria bassiana isolates and one Paecilomyces sp. isolate to infect Nezara viridula adults under laboratory conditions. The lethal concentrations (LC50) of the Egyptian and exotic Beauveria and Paecilomyces isolates for N. viridula were 323 × 106, 835 × 106 and 281 × 107 conidia/ml, respectively. Although, there was no significant difference observed in the mortality rates of adults exposed to the conidiospores of the fungal isolates, the results demonstrated a concentration-dependent pattern. The conidia showed limited attachment to the insect integument. Interestingly, a positive relationship was observed between the rate of increase in the germination of conidia and that of the exposure time, up to 84–92 % at 48 h post-infection. Furthermore, germination of the isolates on the wings was significantly different. The conidia gave rise to germ tubes at 12 h with bipolar germ tubes and hyphal network at 48 h post-infection. SEM revealed that...