Studies on Entomopathogenic Activity of Native Microbial Isolates Against Important Lepidopteran Pests

Abstract

Studies on entomopathogenic activity of native microbial isolates against newlineimportant lepidopteran pests was carried out at the Department of Entomology, newlineUniversity of Agricultural Sciences, Dharwad during 2021-2023. The results of in-vitro newlineevaluation of five different microbial isolates i.e., Streptomyces hyderabadensis, newlineStreptomyces xiaminensis, DBT-90, Streptomyces enissocaesilis and neem leaf newlineendophyte (Streptomyces sp.) against important lepidopteran pests revealed that the newlinehighest larval mortality was recorded in Streptomyces hyderabadensis with 80.00, newline83.33, 76.67 and 70.00 per cent against third instar larvae of Spodoptera litua, Plutella newlinexylostella, Spodoptera frugiperda and Helicoverpa armigera, respectively followed by newlineStreptomyces xiaminensis with 76.67, 80.00, 73.33 and 63.33 per cent mortality at 96 newlinehours after treatment (HAT). Further, these microbial isolates were employed for the newlinefabrication of silver nanoparticles (AgNPs). The formation of AgNPs were confirmed newlinethrough UV-Spectrophotometer, PSA, SEM, EDX and FT-IR spectroscopy. Further, the newlinebiotoxicity of microbial mediated AgNPs was also assessed against third instars of newlineSpodoptera frugiperda. The results indicated that, all the microbial mediated AgNPs newlinecaused effective mortality against S. frugiperda. Among the isolates, S. hyderabadensis newlineand S. xiaminensis based AgNPs (5000 ppm) exhibited 100 per cent mortality at 96 newlineHAT. They also caused pupal deformity and adult malformation at lower newlineconcentrations. S. hyderabadensis based AgNPs also suppressed the growth and newlinenutritional parameters of the larvae effectively. Antifeeding activity of microbial newlinemediated AgNPs revealed the highest antifeedancy with S. hyderabadensis based newlineAgNPs (86.00 %) at 96 HAT. Mechanism of nanoparticles in causing the insect newlinemortality was studied by determining detoxifying enzyme activity. Irrespective of newlinetreatments, Glutathione S-transferases and Carboxylesterases enzyme activity was newlineincreased during 24 HAT; later, it was decreased at 72 HAT as compared to control newlinegroup indi