Toxicological and Biochemical Description of Synergism of Beauveria bassiana and Emamectin Benzoate against Megalurothrips usitatus (Bagrall).

The prophylactic application of synthetic insecticides to manage Megalurothrips usitatus (Bagrall) has resulted in insecticide resistance and negative impacts upon natural ecosystems. This has driven the need for developing alternative pest control strategies. In the present study, we investigated the synergistic interaction between the entomopathogenic fungus Beauveria bassiana and the insecticide emamectin benzoate on M. usitatus. The results of our research exhibited that higher doses of emamectin benzoate inhibited the germination rate and colony growth of B. bassiana. The percentage of M. usitatus mortality following B. bassiana and emamectin benzoate treatment indicated a dose-mortality effect. All concentrations of emamectin benzoate combined with different concentrations of B. bassiana demonstrated a synergistic effect five days post-treatment. When B. bassiana and emamectin benzoate were applied alone or in combination, antioxidant enzyme activities, including acetylcholinesterase, catalase, superoxide dismutase, and peroxidase, were significantly lower in M. usiatus than in the controls at the end of the experimental period. The findings of our study confirm the synergistic effect of B. bassiana and emamectin benzoate on M. usitatus, as well as the biochemical process that might be involved in the regulation of the synergistic effect.

Immune-Related Genes of Megalurothrips usitatus (Bagrall) Against Beauveria brongniartii and Akanthomyces attenuatus Identified Using RNA Sequencing.

Megalurothrips usitatus (Bagrall) is an important pest of legumes worldwide, causing great economic loss every year. Beauveria brongniartii and Akanthomyces attenuatus have shown considerable pathogenicity against M. usitatus in our previous studies. The medial lethal concentration (LC50) and the sublethal lethal concentration (LC25) of B. brongniartii isolate SB010 against M. usitatus were 8.38 × 105 and 1.73 × 105 conidia mL-1, respectively, whereas those of A. attenuatus isolate SCAUDCL-53 against M. usitatus were 4.37 × 105 and 2.97 × 104 conidia mL-1, respectively. This study reports the transcriptome-based explanation of the stress responses of M. usitatus following the application of B. brongniartii and A. attenuatus. The analysis of the transcriptomic data revealed the expression of 254, 207, 195, and 234 immunity-related unigenes by M. usitatus in response to B. brongniartii LC50 (SB1), B. brongniartii LC25 (SB2), A. attenuatus LC50 (V1), and A. attenuatus LC25 (V2), respectively. The biological function and metabolic pathway analyses showed that these unigenes were mainly related to pattern recognition receptors, information transduction factors, and reaction factors, such as scavenger receptor, cytochrome b5, cuticle protein, lysozyme, and serine protease.