Date of this Version
Weisbrod, J. M. (2020). Effects of Pesticide Residue Accumulation on Honey Bee (Apis mellifera L.) Development & Implications for Hive Management. University of Nebraska-Lincoln, Lincoln, NE.
Honey bee (Apis mellifera L.) colonies face annual declines of 40% in the United States. Pesticides play a role in these losses. Pesticide residues picked up from the environment as well as beekeeper-applied compounds may accumulate within the hive. The effects of pesticide accumulation in comb on bee health mitigation of accumulation have not been well-studied. To examine pesticide exposure on health and development, chlorothalonil and the amitraz metabolite N-(2,4-dimethylphenyl) formamidine (DMPF), two pesticides found in hive products, were applied to brood comb. Queen bees were caged onto treated and control comb and egg laying and development were assessed. Adult bee health measures were also examined to determine the indirect effects on worker bee tasks. Results from this study indicates that bee larvae reared in comb with DMPF developed significantly smaller acini within the hypopharyngeal glands.
Exposure to newer chemistries, does not typically result in rapid high losses of worker bees but instead colonies exhibit slow chronic losses over time, indicating impacts may be due to persistent residual effects within the colony. Here, we assessed the use of dead bee traps for monitoring pesticide incidents to identify exposure at the onset. To assess efficacy of traps, worker bees were treated with imidacloprid or freeze-killed bees (positive control) and put back into hives to determine trap recapture rate. Dead bee traps recaptured 27.7% of bees from the positive control group though sub-lethal doses of imidacloprid bees were recovered at significantly lower rates. Traps from three separate apiaries were also monitored weekly to assess seasonal patterns of losses and found distinct differences for each apiary between months in observed abnormal mortality. Results from this study may determine how factors like pesticides can be monitored and may lead to management recommendations. This thesis concludes with a detailed instructional guide for beekeepers to properly build and use them as well as provides other resources to encourage beekeepers to monitor for other hive stressors.
Advisor: Judy Wu-Smart