Investigating the enzymatic response of Plutella xylostella L. (Lepidoptera: Plutellidae) to Metarhizium anisopliae (Metschnikoff) Sorokin (Ascomycota: Hypocreales) Infection: A Comprehensive study

Abstract

The diamondback moth (DBM), Plutella xylostella, poses a significant threat to cruciferous crops due to its resistance to conventional insecticides. Entomopathogenic fungi (EPF), such as Metarhizium anisopliae offer a promising solution for the management of P. xylostella. When exposed to lethal or sub-lethal doses of microbial insecticides especially EPF, insects often mount various immune responses as a survival mechanism, including the activation of detoxification and protective enzymes. In this study, M. anisopliae (Ma1) isolated from soil resulted in 94.00 ± 0.245 percent mortality of DBM at a conidial load of 1 x 10⁹ conidia/ml, with an LC₅₀ value of 2.70 x 10⁶ conidia/ml. The activity of various detoxifying and free radical scavenging enzymes was assessed in whole-body samples of P. xylostella at varying time intervals after inoculation with the entomopathogenic fungi. The results showed that the activity of the enzymes increased after 48 h of inoculation, reaching a maximum at 96 h after inoculation. After 96 h, the activity of these enzymes started to decline significantly. In conclusion, the M. anisopliae isolate Ma1 was found to be highly effective against P. xylostella. Therefore, it could be formulated using appropriate carrier material and used as a component in Integrated pest management programs. Elevated levels of detoxification and free radical scavenging enzyme expression helps in understanding the immune mechanisms in P. xylostella in response to M. anisopliae infection.