Erika Plettner

Varroa destructor Anderson & Trueman (Acari: Varroidae) is an obligatory ectoparasitic mite of honey bees Apis mellifera and Apis cerana (European and Asian honey bees respectively) and is one of the major threats to European honey bee colonies almost worldwide. Chemical signals from the bee are known to play a major role in host detection of V. destructor. Apparently, specific chemosensing of V. destructor allows it to distinguish between bees of different age and tasks. Our approach to provide control measures against the mite includes the interference in Varroa-host detection via the disruption of the host identification/orientation process by the mite. In search for a compound that specifically disrupts the interaction between the V. destructor and its host, we developed a method to study the chemosensing of Varroa using its main olfactory organ situated on the foreleg. Using the electrophysiological assay on isolated foreleg we screened putative chemosensory disruptive compounds. In particular, we examined the effect of volatile compounds originally developed for disruption of pheromone detection by moths and a commercially available repellent N,N-Diethylmeta-toluamide DEET. The effect of disruptive compounds was further tested on host location by mites. Two types of electrophysiological effects were evaluated on isolated foreleg: short term inhibition and long term inhibition. Using this approach, several potent chemosensory disrupting compounds for the Varroa were identified, thus opening new avenues for the control of this major honeybee pest.