Honey bees contribute an estimated 15 billion dollars to the US economy per year in the form of supplementary agricultural services (i.e., pollinating). However, honey bee colony health can be adversely affected by many pesticides currently in use and mite infections in the colony. Of particular interest is a pyrethroid pesticide called tau-fluvalinate, which is relatively non-toxic to honey bees yet still potent against many other insects, like the parasitic varroa mites that commonly infect honey bee colonies. Honey bees’ resistance to tau-fluvalinate is derived from their unique enzymes that catalyze the breakdown of aromatic rings, a particular chemical compound that occurs on molecules of tau-fluvalinate more than on other kinds of pyrethroids.Edit Summary
“Although some pyrethroids, such as cyfluthrin and lambda-cyhalothrin, are highly toxic to honey bees, the toxicity of tau-fluvalinate is low enough to warrant its use to control parasitic mites inside honey bee colonies…metabolic detoxification, especially that mediated by [cytochrome] P450s [enzymes], contributes significantly to honey bee tolerance of pyrethroid insecticides…Pyrethroids…are neurotoxicants that exert their insecticidal effect by prolonging the open phase of the sodium channel…The toxicity of pyrethroids to honey bees ranges from relatively low…to highly toxic…to extremely toxic. The relatively low toxicity of tau-fluvalinate…to honey bees has allowed its successful use as an acaricide applied inside hives to control parasitic varroa mites.” (Johnson 2006:1046).
“Results suggest that enzyme-mediated detoxification is important in the tolerance of honey bees to pyrethroid insecticides. Inhibition of P450s with PBO [piperonyl butoxide] significantly enhanced the toxicity of all three pyrethroids tested…the wide use of tau-fluvalinate as a bee-safe miticide is based on its rapid detoxification by P450s…One of the numerous reactions catalyzed by P450s is the oxidation of aromatic rings. The additional aromatic ring on tau-fluvalinate and flumethrin may present an additional site for modification by P450s…Identification of specific detoxification enzymes responsible for honey bee metabolism of pyrethroids may provide opportunities for the design of new pesticides with lower bee toxicity without compromising efficacy of mite control.” (Johnson 2006:1048, 1049).