Larvicidal potential of irradiated myco-insecticide from Metarhizium anisopliae and larvicidal synergistic effect with its mycosynthesized titanium nanoparticles (TiNPs)

Abstract

This work was undertaken to investigate the effect of different dose levels of gamma irradiation ranged from 0.2 to 1 kGy on Metarhizium anisopliae lipase, protease, amylase and nitrate reductase activities. The optimum results obtained with a dose level 0.4 kGy which stimulated the maximum enzymatic activities. Titanium nanoparticles (TiNPs) were mycosynthesized using unirradiated and irradiated (0.4 KGy) M. anisopliae and characterized using UV–Vis spectrophotometry, electron microscopy (TEM) and energy-dispersive spectrometry (EDX). In addition, the difference between the growing of unirradiated and irradiated M. anisopliae on larval cuticle was studied using scanning electron microscopy. In Insecticidal activity of unirradiated and irradiated M. anisopliae with and without their mycosynthesized TiNPs were also examined against Galleria mellonella larvae and the highest larvicidal activity was obtained from the combination of irradiated M. anisopliae with its mycosynthesized TiNPs and that may be due to the higher fungal enzymatic activities, higher TiNPs concentration and lower TiNPs size. The synergistic studies revealed that there is a synergistic larvicidal relationship between irradiated M. anisopliae cells and their mycosynthesized TiNPs with a synergistic factor (SF) of 1.6 and 4.2 for LC50 and LC90, respectively. This study provided the first report of the synergistic effect between irradiated M. anisopliae and their mycosynthesized TiNPs. Such a combination could represent an effective approach for reducing the likelihood of increased insect resistance to entomopathogenic fungi. Keywords: Entomopathogenic fungi, Metarhizium anisopliae, Titanium nanoparticles, Galleria mellonella