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

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. 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. 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.