Efficacy of two Metarhizium anisopliae isolates and the nano-fungus Metarhizium anisopliae@Fe3O4 against Diamondback moth

Diamondback moth (DBM), Plutella xylostella (L.) is one of the most destructive insect pests of brassicaceous crops in Iran and throughout the world. Chemical pesticides play a key role in managing DBM, however, the adverse effects of chemical insecticides and the significant resistance of the pest to the broad range of synthetic insecticides has led to increased attention to the use of safe and eco-friendly components. Therefore, in this research we examined pathogenicity of two Metarhizium anisopliae isolates (AM111 & AH112) and synthesized Metarhizium anisopliae AM111@Fe3O4 against the 3rd instar larva of diamondback moth under laboratory conditions. Toxicity comparisons of nano-formulated fungus and non-formulated one demonstrated a significant decrease in the LC50 value of Metarhizium anisopliae AM111@Fe3O4 estimated as 2.5 × 104 conidia/ ml that exhibited nano-formulated fungus was more efficient against the pest. Mean comparisons of pure and formulated fungus repellencies showed that nano-fungus significantly was more repellent against the third instar larvae of DBM, so mean repellency values of non-formulated fungus and nano-fungus on 3rd instar larvae of DBM were equivalent to 69 and 74.66%, respectively. Also, in enzymatic study, protease Pr1 activity comparisons in optimal pH (=11) exhibited significant difference between control and fungal treatment and the most level of Pr1 activity was observed in fungal treatment. Pr1 activity levels in nano-fungus and non-formulated fungus treatments were equivalent to 2.994 and 0.051 mg/ml, respectively. Our results showed that nano-fungus was more effective on P. xylostella relative to pure-fungus and Metarhizium anisopliae AM111@Fe3O4 can be used as an efficient new component in integrated P. xylostella management.