Identification and evaluation of isolated entomopathogenic fungus from Egyptian soil against the black cutworm larvae of Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

Abstract

Abstract Background The black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is considered as one of the most destructive pests of many field crops in Egypt. Entomopathogenic fungi (EPF) have long been accepted as relatively safe alternatives to chemical insecticides. In the past decades, many researchers have compared the effective local isolates of EPF to the formulated product of the same fungus and reported that local isolates were more efficient than formulations when used against target insects. Results The present study discussed the pathogenic activity of local isolate after scientific characterization. Two insect species [Galleria mellonella L. and Agrotis ipsilon (Hufn.)] were used in this evaluation. The fungus was isolated from soil samples by trapping method, and fourth-instar larvae of Galleria were used to evaluate the pathogenicity of the isolate. The isolate was identified as Beauveria bassiana. Different levels of the fungus development depending on the test temperatures (20, 25, 30, 35 and 40 °C) were tested. Optimal growth of the isolate fungus was recorded at 25 °C. The corrected mortality rate for fourth-instar larvae of G. mellonella treated with the isolate spores at 6.4 × 105 spores/ml was (96%) after 10 days, while the mortality of last instar larvae of A. ipsilon was (48 and 100%) at the concentrations of 9.2 × 104 and 2.9 × 106 spores/ml, respectively, after 14 days compared to (24%) in the control. Both pupation and the sex ratio in adults were affected at different levels according to the concentration. The effect was also very clear in the increased rates of malformation in adults. Conclusion The EPF, B. bassiana, isolated from the soil, was highly effective against G. mellonella larvae in storage and A. ipsilon larvae in soil; therefore, it could be recommended as an alternative control agent for chemical pesticides.