Synergism between Hydramethylnon and Metarhizium anisopliae and Their Influence on the Gut Microbiome of Blattella germanica (L.)

Abstract

(1) Background: The widespread use of insecticides has cause extensive resistance in German cockroach (Blattella germanica) populations globally. Biological control has the potential to mitigate insecticide resistance, and Metarhizium anisopliae (Meschn.) Sorokin, an entomopathogenic fungus, alone and in combination with various insecticides, has shown good effects against cockroaches. (2) Methods: This experiment compared the cumulative mortality after infecting B. germanica with M. anisopliae conidia by two routes, per os and topical application. To probe the mechanisms that underlie the synergism between M. anisopliae and hydramethylnon, we conducted dose–response assays with cockroaches fed combinations of M. anisopliae and hydramethylnon and characterized the gut microbiomes of the treated cockroaches. (3) Results: The study showed that the mortality with per os infection was lower than that with topical application. In addition, the combination of M. anisopliae and hydramethylnon had a synergistic effect in 16 treatments. The gut microbiome was also altered by hydramethylnon treatment. The abundance of Parabacteroides and Enterococcus declined with the hydramethylnon and combination treatments, which are known to have anti-inflammatory and antifungal activities. The abundance of Alistipes, which is a fungal cell wall component, significantly increased in these treatments. (4) Conclusions: Therefore, we speculate that the major mechanism underlying this synergism is hydramethylnon promoting the survival of M. anisopliae in the harsh gut environment and enhancing its virulence for German cockroaches by altering the gut microbiome. This may provide a method for the fight against B. germanica and lay the foundation for the development of new baits.

Metarhizium anisopliae is a valuable grist for biocontrol in beta‐cypermethrin‐resistant Blattella germanica (L.)

“…58 This result indicates that the gut microbiota of German cockroaches is disordered after M. anisopliae infection. 59 In addition, the mortality of the conventional cockroach of the R and S strains was lower than that of the germ-free cockroach. The gut microbiota enhances resistance to widely used pathogenic microorganisms.…”

“…The commensal bacterium Enterococcus faecium triggers enhanced pathogen resistance and intestinal tract epithelial barrier function via secreted peptidoglycan hydrolase (SagA) 58 . This result indicates that the gut microbiota of German cockroaches is disordered after M. anisopliae infection 59 . In addition, the mortality of the conventional cockroach of the R and S strains was lower than that of the germ‐free cockroach.…”

Screening of Fungal Strains and Formulations of Metarhizium anisopliae to Control Phyllotreta striolata in Chinese Flowering Cabbage

“…Several studies have reported the combination synergisms of Ma with chemicals. For example, Ma and chlorantraniliprole exhibited a synergistic effect against Spodoptera litura larvae [ 28 ], Ma and imidacloprid were synergistic against Cyrtomenus bergi nymphs [ 29 ], while Ma and hydramethylnon had synergism with German cockroaches [ 30 ]. This study is the first to demonstrate the synergism of Ma and Chl against CFB adults.…”

Anti-oviposition and repellence of Cordyceps fumosorosea against Spodoptera exigua

“…Rahim et al (2013) mentioned that the whitefly (Bemisia tabaci) was infected at all stages of development with a concentration of EPF at 10 6 conidia per mL. The same concentration of 10 6 conidia per mL was lower compared to those between 10 8 and 10 10 conidia per mL, which are often used in commercial formulations and relates to real-life applicability or applications (Soliman et al 2019;Chao et al 2020).…”