Preliminary studies on the susceptibility level of Ceutorchynhus assimilis (Coleoptera: Curculionidae) to acetamiprid and chlorpyrifos in Poland and resistance mechanisms of the pest to acetamiprid.

The cabbage seed weevil, Ceutorchynhus assimilis (Paykull) (Coleoptera: Curculionidae) is a pest that more and more often causes large financial losses for rapeseed cultivators in Poland and other European countries. One of the reasons of these problems is the resistance of the pest to certain active substances of insecticides. The aim of the study was to assess the susceptibility level of the pest to chlorpyrifos, an organophosphate substance, and acetamiprid, a neonicotinoid, and to determine its enzymatic mechanisms of susceptibility to acetamiprid using synergists, i.e., blockers of particular enzyme groups. The presented research is the first to discuss the mechanisms of the resistance of the cabbage seed weevil to acetamiprid. The achieved results showed medium, high, or very high resistance of the cabbage seed weevil to acetamiprid and its lack of resistance to chlorpyrifos. The research on the mechanisms of the resistance of the pest to acetamiprid revealed the participation of hydrolytic enzymes blocked by S,S,S-tributylphosphorotrithioate and glutathione transferases blocked by diethyl malonate in the metabolism of acetamiprid. The results did not show the participation of oxidative enzymes and esterases blocked by piperonyl butoxide in the detoxification of acetamiprid.

The effect of a piperonyl butoxide/tau-fluvalinate mixture on pollen beetle (Meligethes aeneus) and honey bees (Apis mellifera).

BACKGROUND: Previous work has characterised pyrethroid resistance in pollen beetle (Meligethes aeneus F.) as principally an oxidative mechanism. Piperonyl butoxide (PBO) can synergise this resistance in the field, but its effects on the honey bee are thought to be unacceptable. RESULTS: A field trial in Poland was conducted to show that a mixture of PBO and tau-fluvalinate at the registered rate gave increased and longer-lasting control of resistant pollen beetle. Four days after spraying with tau-fluvalinate, only 20% of pollen beetles were controlled, compared with 70% if the tau-fluvalinate/PBO mixture was used. No detriment to honey bee health was observed using the same mixture. CONCLUSIONS: PBO, if used in conjunction with a pyrethroid of relatively low bee toxicity, can successfully overcome pyrethroid resistance in pollen beetle without incurring an increased loss of honey bees, even if they are present at the time of spraying.

Characterising metabolic resistance in pyrethroid-insensitive pollen beetle (Meligethes aeneus F.) from Poland and Switzerland.

BACKGROUND: Pollen beetle (Meligethes aeneus F.) has become the most important pest of oilseed rape in Europe, but its control has been greatly hindered by pyrethroid resistance. Target-site resistance has been implicated previously, and, whilst synergism has been found with piperonyl butoxide (PBO), the exact nature of metabolic resistance has remained unknown. The use of PBO, in conjunction with its analogue EN 16/5-1, has allowed the characterisation of metabolic resistance. RESULTS: In vitro assays in combination with in vivo studies using PBO and EN 16/5-1 showed that high synergism of pyrethroids was primarily correlated with an oxidative mechanism, although a limited contribution by esterases was implicated in one population. CONCLUSION: Differential synergism has enabled the characterisation of pyrethroid resistance in populations of M. aeneus. It was found to be principally due to an oxidative-based mechanism, and, if a synergist were to be used to inhibit this enzyme group, renewed control against resistant pests could be achieved.