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Research Project: Determining the Impacts of Pesticide- and Nutrition-Induced Stress on Honey Bee Colony Growth and Survival

Location: Honey Bee Research

Title: Effects of oral exposure to fungicides on honey bee nutrition and immunity

Author
item Degrandi-hoffman, Gloria
item Chen, Yanping - Judy
item Watkins De Jong, Emily
item Chambers, Mona
item Hidalgo, Geoffrey

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2015
Publication Date: 8/28/2015
Citation: Hoffman, G.D., Chen, Y., Watkins De Jong, E.E., Chambers, M.L., Hidalgo, G. 2015. Effects of oral exposure to fungicides on honey bee nutrition and immunity. Journal of Economic Entomology. doi: 10.1093/jee/tov251.

Interpretive Summary: Honey bees can be exposed to fungicides during pollination because these pesticides can be applied while crops are in bloom. Unlike insecticides that affect neurological function, fungicides disrupt or inhibit fundamental cellular processes such as respiration. The biochemical pathways affected by fungicides are conserved across species so that the modes of action for fungicides might have analogous biochemical or physiological effects on non-fungal organisms such as bees. We found that the fungicides boscalid and pyraclostrobin reduce levels of ATP in thoracic muscle tissue. They also caused reduced pollen consumption and protein digestion and increased virus titers. This combination of effects might contribute to colony losses by increasing the vulnerability of bees to additional stressors such as poor nutrition, Varroa, and other pathogens.

Technical Abstract: Worker bees fed pollen containing fungicides (boscalid and pyraclostrobin) that are respiratory inhibitors had lower ATP concentrations in thoracic muscle tissue than those fed untreated pollen in both cage and colony studies. Midgut protease activity, used an indicator of consumption, was higher in bees fed fungicide treated pollen in cage and colony studies indicating reduced consumption of the fungicide-treated pollen. Bees not only consumed less treated pollen, but also digested less of the protein in it than controls. Deformed wing virus titers were higher in treatment bees than in controls, suggesting that feeding on pollen contaminated with the fungicide could reduce innate immunity. The combination of effects identified here indicates that the fungicides investigated in this study could reduce worker longevity perhaps due to malnutrition and compromised immunity. This could weaken colonies and make them vulnerable to additional stressors such as nutritional stress, Varroa, and other pathogens.