In the same issue:

Synergistic Interactions Between In-Hive Miticides in Apis mellifera
Authors: Johnson, Reed M.; Pollock, Henry S.; Berenbaum, May R.
Source: Journal of Economic Entomology, Volume 102, Number 2, April 2009 , pp. 474-479(6)

Abstract:
> The varroa mite, Varroa destructor Anderson & Trueman, is a devastating pest of honey bees, Apis 
mellifera L., that has been primarily controlled over the last 15 yr with two in-hive miticides: the 
organophosphate coumaphos (Checkmite+), and the pyrethroid tau-fluvalinate (Apistan). Both 
coumaphos and tau-fluvalinate are lipophilic compounds that are absorbed by the wax component of 
the hive, where they are stable and have the potential to build up over repeated treatments such 
that bees could be exposed to both compounds simultaneously. Although these compounds were 
chosen as in-hive miticides due to their low toxicity to honey bees, that low toxicity depends, at least 
in part, on rapid detoxification mediated by cytochrome P450 monooxygenase enzymes (P450s). In 
this laboratory study, we observed a large increase in the toxicity of tau-fluvalinate to 3-d-old bees 
that had been treated previously with coumaphos, and a moderate increase in the toxicity of 
coumpahos in bees treated previously with tau-fluvalinate. The observed synergism may result from 
competition between miticides for access to detoxicative P450s. 

*** These results suggest that honey bee mortality may occur with the application of otherwise 
sublethal doses of miticide when tau-fluvalinate and coumaphos are simultaneously present in the 
hive. ***

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