Combined effect of the entomopathogenic fungusMetarhizium robertsiiand avermectins on the survival and immune response ofAedes aegyptilarvae

Abstract

Combination of insect pathogenic fungi and microbial metabolites is a prospective method for mosquito control. The effect of the entomopathogenic fungus Metarhizium robertsii J.F. Bischoff, S.A. Rehner & Humber and avermectins on the survival and physiological parameters of Aedes aegypti (Linnaeus, 1762) larvae (dopamine concentration, glutathione S-transferase (GST), nonspecific esterases (EST), acid proteases, lysozyme-like, phenoloxidase (PO) activities) was studied. It is shown that the combination of these agents leads to a synergistic effect on mosquito mortality. Colonization of Ae. aegypti larvae by hyphal bodies following water inoculation with conidia is shown for the first time. The larvae affected by fungi are characterized by a decrease in PO and dopamine levels. In the initial stages of toxicosis and/or fungal infection (12 h posttreatment), increases in the activity of insect detoxifying enzymes (GST and EST) and acid proteases are observed after monotreatments, and these increases are suppressed after combined treatment with the fungus and avermectins. Lysozyme-like activity is also most strongly suppressed under combined treatment with the fungus and avermectins in the early stages posttreatment (12 h). Forty-eight hours posttreatment, we observe increases in GST, EST, acid proteases, and lysozyme-like activities under the influence of the fungus and/or avermectins. The larvae affected by avermectins accumulate lower levels of conidia than avermectin-free larvae. On the other hand, a burst of bacterial CFUs is observed under treatment with both the fungus and avermectins. We suggest that disturbance of the responses of the immune and detoxifying systems under the combined treatment and the development of opportunistic bacteria may be among the causes of the synergistic effect.

Fungus Metarhizium robertsii and neurotoxic insecticide affect gut immunity and microbiota in Colorado potato beetles

“…These interactions may cause a synergistic effect between the fungus and the avermectins. It should be noted that similar alterations of the detoxification enzyme activities under the combined action of M. robertsii and avermectins were established on mosquito Aedes aegypti larvae at the initial stages of mycosis and toxicosis 71 , which is in keeping with our hypothesis.…”

Influence of Bacillus thuringiensis and avermectins on gut physiology and microbiota in Colorado potato beetle: Impact of enterobacteria on susceptibility to insecticides

“…A similar effect was found in mosquito larvae after their simultaneous treatment with avermectins and M . robertsii conidia, which accumulated in the mosquito guts [ 63 ]. In particular, under the influence of avermectins, the CFU count of the fungus in the larvae significantly decreased.…”

Mosquito-Borne Diseases Emergence/Resurgence and How to Effectively Control It Biologically

“…Particular attention has been paid to fungal species belonging to the genera Lagenidium, Coelomomyces, Entomophthora, Culicinomyces, Beauveria, and Metarhizium for their power to reduce mosquito populations, but unfortunately, none of them have been specifically adapted as larvicidal agents against important vector species [109][110][111], even transgenic ones [112]. Application to surfaces on which mosquitoes land or need to pass through, such as fungus-impregnated cloths around bed nets, attractive bait stations, and adult mosquito traps and PET traps, show promising results, with a 39-50% reduction in survival rates of malaria-carrying mosquitoes and elimination of 95% of Anopheles arabiensis mosquitoes in a bait station [113].…”