Синергетическое действие пиретроидного инсектицида и энтомопатогенного гриба на Daphnia magna Straus

The interaction between the entomopathogenic fungus Metarhizium robertsii and the pyrethroid insecticide esfenvalerate on Daphnia magna Straus was investigated. A synergy in the mortality of daphnids was detected after simultaneous treatment with sub-lethal doses of the fungus (1×10 5 conidia/ml) and esfenvalerate (0.1 mkg/l). The defense strategies of daphnids infected by fungus and treated with esfenvalerate and untreated insects were compared to investigate the mechanisms of this synergy. Activity of enzymes of the detoxification system and concentration of dopamine were measured. We have shown changes in the activities of the enzymes and dopamine concentration of daphnids under combined treatment of esfenvalerate and fungus. Fungus enhanced activity of glutathione-S-transferase and non-specific esterase but did not affect the dopamine level. Esfenvalerate inhibited the activity of enzymes in the detoxification system and cause a rise in dopamine level. We assume that the suppression of the detoxification system may be one of the reasons of synergy between M. robertsii and esfenvalerate.