BackgroundThe ectoparasitic mite, Varroa destructor, is considered to be one of the most significant threats to apiculture around the world. Chemical cues are known to play a significant role in the host-finding behavior of Varroa. The mites distinguish between bees from different task groups, and prefer nurses over foragers. We examined the possibility of disrupting the Varroa – honey bee interaction by targeting the mite's olfactory system. In particular, we examined the effect of volatile compounds, ethers of cis 5-(2′-hydroxyethyl) cyclopent-2-en-1-ol or of dihydroquinone, resorcinol or catechol. We tested the effect of these compounds on the Varroa chemosensory organ by electrophysiology and on behavior in a choice bioassay. The electrophysiological studies were conducted on the isolated foreleg. In the behavioral bioassay, the mite's preference between a nurse and a forager bee was evaluated.Principal findingsWe found that in the presence of some compounds, the response of the Varroa chemosensory organ to honey bee headspace volatiles significantly decreased. This effect was dose dependent and, for some of the compounds, long lasting (>1 min). Furthermore, disruption of the Varroa volatile detection was accompanied by a reversal of the mite's preference from a nurse to a forager bee. Long-term inhibition of the electrophysiological responses of mites to the tested compounds was a good predictor for an alteration in the mite's host preference.ConclusionsThese data indicate the potential of the selected compounds to disrupt the Varroa - honey bee associations, thus opening new avenues for Varroa control.

-Honey bees and their ectoparasite Varroa destructor communicate through chemical signals among themselves, but they also eavesdrop on each other's chemical cues. We summarize semiochemicals of honey bees and Varroa , and their roles in honey bee-Varroa interactions. We also give an overview of current Varroa control methods, which can be classified into three categories: (1) chemical control methods with acaricides, (2) biotechnical intervention, and (3) bee breeding programs. Widely used synthetic chemical acaricides are failing due to the emergence of resistant mites. Therefore, new methods are being sought for Varroa control, and methods that target the semiochemical interactions between bees and mites are among the candidates. We review our discovery of compounds that alter the host choice of Varroa mites (from nurse to forager) in laboratory tests. Any semiochemicalbased methods are still in the experimental stage and need validation in the field.Apis mellifera / Varroa destructor / mite control / chemical senses / semiochemical

To study the binding mechanism of disparlure (7,8)‐epoxy‐2‐methyloctadecane enantiomers with pheromone‐binding proteins (PBPs) of the gypsy moth, oxygen‐17 or 18 and 5,5,6,6‐deuterium labelled disparlure enantiomers were prepared in an efficient, enantioselective route. Key steps involve the asymmetric α‐chlorination of dodecanal by SOMO catalysis and Mitsunobu inversion of a 1,2‐chlorohydrin. The pheromone, (+)‐disparlure (7R, 8S), was tested in two infested zones, demonstrating that it is very attractive towards male gypsy moths. Studies of the binding of (+)‐disparlure and its antipode to gypsy moth PBPs by 2H &17O NMR at 600 MHz are reported. Chemical shifts, spin‐lattice relaxation decay times (T1) and transverse relaxation decay times (T2) of deuterium atoms of disparlure enantiomers in 2H NMR show that the binding of disparlure enantiomers to PBP1 differs from binding to PBP2, as expected from their opposite binding preferences (PBP1 binds (–)‐disparlure, and PBP2 binds (+)‐disparlure more strongly). Models of the disparlure enantiomers bound to one internal binding site and two external binding sites of both PBPs were constructed. The observed chemical shift changes of deuterated ligand signals, from non‐bound to bound, T1 and T2 values are correlated with results from the simulations. Together these results suggest that the disparlure enantiomers adopt distinct conformations within the binding sites of the two PBPs and interact with residues that line the sites.

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