Effects of the Entomopathogenic Fungus Metarhizium anisopliae on the Mortality and Immune Response of Locusta migratoria.

Entomopathogenic fungi are the key regulators of insect populations and some of them are important biological agents used in integrated pest management strategies. Compared with their ability to become resistant to insecticides, insect pests do not easily become resistant to the infection by entomopathogenic fungi. In this study, we evaluated the mortality and immune response of the serious crop pest after exposure to a new entomopathogenic fungus strain, CQMa421. CQMa421 could effectively infect and kill the adults and nymphs. The locust LT under 1 × 10 conidia/mL concentration of was much lower than that under conidial concentration 1 × 10 conidia/mL (i.e., 6.0 vs 11.2 and 5.0 vs 13.8 for adults and nymphs, respectively). The LC (log) of against locust adults and nymphs after 10 days was 5.2 and 5.6, respectively. Although the number of hemocytes in after exposure to did not differ with that in the controls, the enzymatic activity of superoxide dismutase (SOD) and prophenoloxidase (ProPO) did differ between the two treatments. The activities of both SOD and ProPO under the treatment were lower than that in the controls, except for the ProPO activity at 72 h and the SOD activity at 96 h. Further, the expression of the immune-related genes defensin, spaetzle, and attacin differed after exposure to for 24 h to 96 h. Taken together, this study indicated that infection with CQMa421 could cause the death of by interacting with the immune responses of the host, demonstrating that this fungal strain of can be an efficient biocontrol agent against .