COLONY COLLAPSE: THE COST OF VARROA DESTRUCTOR IN APIS MELLIFERA REPRODUCTION

The aim of this thesis is to develop a better understanding of how parasite load, resource levels, and temperature affect the reproduction of Western honey bee (Apis mellifera) colonies. Many studies have covered extensively the damaging effects of the parasitic mite Varroa destructor on colony health, resulting from weakening of immature brood, premature transitioning of adults to higher mortality roles within the colony, and decreasing levels of incoming resources due to reduced workers’ foraging capacity. It can be assumed then, that under these conditions, there are trade-offs across behaviors where bees must divert time and energy that could be used for brood care and resource acquisition to engage in grooming and hygienic behaviors to keep parasite load down. A series of multivariate regression analyses were performed to explore the dynamics at play in this host-parasite relationship. For the response variable, a measure of honey bee reproduction (number of frames containing brood) dependent on the type of inspection performed (Full or Quick) was used. Predictive variables included measures of parasite load using daily mite counts and two separate models (pollen and honey) to hold resources constant. A third independent variable, temperature, was used to control for variation of honey bee reproduction over the year. Results show resources have a positive significant effect on the number of frames containing brood of any type across both models and inspection types, except for frames containing larvae in the pollen model. The number of mites per day may also have an effect on the number of frames containing sealed brood but a larger sample size is needed to observe significance.