Mortality and immune challenge of a native isolate of Beauveria bassina against the larvae of Glyphodes pyloalis Walker (Lepidoptera: Pyralidae)

Abstract

Abstract Background Entomopathogenic fungi (EPF) attack a wide range of insects. They are considered environmental friendly alternatives to synthetic insecticides for pest control. In the present study, virulence of a native isolate of the EPF, Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae) was evaluated against the least mulberry pyralid, Glyphodes pyloalis Walker (Lepidoptera: Crambidae), through bioassay, pathogenic pathways, and immune responses. Results The values of 2.6 × 104 conidia/ml and 3.54 days were determined as the median lethal concentration (LC50) and median lethal concentration (LT50) of AM-118 against the 4th instar larvae of G. pyloalis, respectively. The activities of proteases and chitinases in the culture medium containing the larval cuticle were higher than the control medium. Moreover, the total and the differential hemocyte counts of the larvae were significantly changed after injection with AM-118 spores. The highest numbers of total hemocytes and granulocytes were obtained 3 and 6 h post-injection, while the highest numbers of plasmatocytes and nodules were observed 6 h post-injection. The highest activity of phenoloxidase was determined 12 h post-injection by AM-118 spores. Conclusions The findings imply on virulence of the AM-118 isolate against the larvae of G. pyoalis although immune responses were triggered by the spores.

Keywords

• Glyphodes pyloalis
• Beauveria bassiana
• Immunity
• Mycoinsecticides
• Virulence