Assessing the efficacy of un and gamma-irradiated entomopathogenic nematode, Steinernema carpocapsae as an eco-friendly approach to control Agrotis ipsilon larvae

Abstract

The black cutworm, Agrotis ipsilon (Hufnagel) is one of the most devastating agricultural pests that attack different crops worldwide. Entomopathogenic nematodes (EPNs) have been utilized in classical, conservation, and augmentative biological control programs. Consequently, this study was designed to estimate the efficacy of an unirradiated and gamma-irradiated entomopathogenic nematode, Steinernema carpocapsae (all), against A. ipsilon larvae as a safe control tool to reduce chemical environmental hazards. The virulence of different concentrations (10, 20, 30 and 40 IJs/ml) of unirradiated and gamma-irradiated (with 2 Gy) of S. carpocapsae was evaluated. Changes in peroxidase (Px) and polyphenyl oxidase (PPO) zymographic patterns were also investigated after larvae were treated with LC50 values for S. carpocapsae. The results revealed that larval mortality increased with increasing S. carpocapsae concentration and time after treatment. The 2 Gy gamma-irradiated S. carocapsae caused a greater pathogenic effect than the unirradiated S. carocapsae, where the LC50 values of 2 Gy gamma-irradiated S. carocapsae were 31.19 and 17.78 IJs/ml after 1 and 2 days, respectively, compared to 113.23 and 65.83 IJs/ml for unirradiated S. carocapsae. For the toxicity index, gamma irradiation at a dose of 2 Gy was selected and given an arbitrary 100 units and considered a standard treatment. Analysis of gel electrophoresis revealed 3 bands of Px and PPO in control larvae; treatment with unirradiated and irradiated S. carpocapsae caused the disappearance of the first band of both enzymes and lowered the intensity of the other 2 bands. The laboratory studies revealed that 2 Gy gamma-irradiated S. carpocapsae could be used as an eco-safe management tool against A. ipsilon larvae under field conditions.