Examining Varroa-resistant Honey Bee Queens from Commercial Breeders: Colony Productivity, Hygienic Behavior, Suppression of Mite Reproduction, and the Relationship of Juvenile Hormone III to Mite Abundance

This research was conducted to assess the performance of commercially bred honey bee queens sold as resistant to the parasitic mite, Varroa destructor. The study’s objectives were to: 1) Compare honey and pollen stores and V. destructor infestation in colonies established with hybrid Russian, SMR, and control queens, 2) Determine levels of hygienic behavior and mite non-reproduction in the same colonies, and 3) Determine the relationship between juvenile hormone III in honey bee larvae and V. destructor reproduction.

In Part One, when honey, pollen, and V. destructor levels were measured, no significant differences were found among types of queens. The similarity of V. destructor levels among study colonies with hybrid queens suggests that hybridization has diminished the effectiveness of the mite-resistance found in artificially inseminated mite-resistant queens.

In Part Two, two traits associated with mite tolerance in honey bee colonies were measured, hygienic behavior and mite non-reproduction. Again, no significant differences were found in the levels of either trait among queen types. However, significant relationships were found between both traits and V. destructor concentrations in the colonies at the end of the season.

Data suggest that, while the levels of resistant traits in hybrid SMR and Russian queens available from commercial breeders do not differ significantly from controls, these traits are present in the honey bee population as a whole and contribute to lower parasite infestations.

In Part Three, the possible influence of honey bee juvenile hormone III levels on V. destructor reproduction was examined. A short test was conducted to determine juvenile hormone titers during the honey bee’s fifth larval instar, a period coincident with initial mite feeding. Radioimmunoassay was used to detect juvenile hormone in the bees’ hemolymph.

Positive relationships were found between juvenile hormone titers and V. destructor reproduction and between juvenile hormone titers and V. destructor concentration in the colonies at the end of the season. Results suggest that low host juvenile hormone levels might diminish the reproductive capacity of the Varroa mite, both in terms of absolute non-reproduction and in reduced fecundity.

Recommendations are made to queen breeders for the increased use of Varroa-resistant drones in mating yards to ensure the preservation of resistant traits in hybrid queens. Broader studies of juvenile hormone and V. destructor reproduction are also recommended.