No abstract

Summary — A bioassay has been developed to assess the susceptibility of Varroa mites to fluvalinate, flumethrin and acrinathrin. No significant differences were found among groups of mites from the same origin but from different brood stages (capped larvae, pupae with white eyes, pupae with dark eyes and white or pale bodies), while a rather variable response was observed when mites from adult bees were assayed. The LC 50 of mites from areas where treatments with fluvalinate are no longer effective was about 25-50 times higher than that of susceptible mites; an even larger increase in the LC 95 was found. The LC 50 of flumethrin and acrinathrin on mites surviving Apistan treatments increased 10-60 times.

The parasitic mite, Varroa destructor, is the most important threat for apiculture in most bee-keeping areas of the world. The mite is carried to the bee brood cell, where it reproduces, by a nurse bee; therefore the selection of the bee stage by the parasite could influence its reproductive success. This study investigates the role of the cuticular hydrocarbons of the European honeybee (Apis mellifera) in host-selection by the mite. Preliminary laboratory bioassays confirmed the preference of the varroa mite for nurse bees over pollen foragers. GC-MS analysis of nurse and pollen bees revealed differences in the cuticular hydrocarbons of the two stages; in particular, it appeared that pollen bees have more (Z)-8-heptadecene than nurse bees. Laboratory experiments showed that treatment of nurse bees with 100 ng of the pure compound makes them repellent to the varroa mite. These results suggest that the mite can exploit the differences in the cuticular composition of its host for a refined selection that allows it to reach a brood cell and start reproduction. The biological activity of the alkene encourages further investigations for the development of novel control techniques based on this compound.

No abstract

No abstract