Can supplementary pollen feeding reduce varroa mite and virus levels and improve honey bee colony survival?

Authors: DeGrandi-Hoffman, Gloria; Corby-Harris, Vanessa; Chen, Yanping - Judy; Graham, Richard; Chambers, Mona; Watkins De Jong, Emily; Ziolkowski, Nicholas; KANG, YUN - Arizona State University; Gage, Stephanie; Deeter, Megan; Simone-Finstrom, Michael; De Guzman, Lilia

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2020
Publication Date: 10/30/2020
Citation: Hoffman, Gloria D., Corby-Harris, Vanessa L., Chen, Yanping, Graham, Henry, Chambers, Mona L., Watkins De Jong, Emily E., Ziolkowski, Nicholas F., Kang, Yun, Gage, Stepanhie L., Deeter, Megan E., Simone-Finstrom, Michael, De Guzman, Lilia, I. 2020. Can supplementary pollen feeding reduce varroa mite and virus levels and improve honey bee colony survival?. Experimental and Applied Acarology. 82:455-473. https://doi.org/10.1007/s10493-020-00562-7.
DOI: https://doi.org/10.1007/s10493-020-00562-7

Interpretive Summary: Varroa and the viruses they transmit are a major cause of colony losses worldwide. Nutritionally stressed colonies that are infested with Varroa often perish during the winter. Perhaps than, improving colony nutrition could improve the survival chances of colonies infested with Varroa. To test this possibility, we measured Varroa populations and virus levels in colonies with and without supplemental pollen feeding from July to December. Colonies fed supplemental pollen had significantly larger populations than unfed colonies and had higher survival rates. However, feeding pollen did not affect levels of Varroa infestation or deformed wing virus (DWV). Varroa populations were similar between fed and unfed colonies, and were correlated with the frequency of capturing foragers with mites (FWM) at colony entrance. FWM were captured with similar frequency in fed and unfed colonies. DWV levels increased as Varroa populations grew in colonies with or without supplemental pollen feeding. Interestingly, FWM had DWV levels that were similar to those of nurse bees, and significantly lower than foragers without mites. These findings suggest that FWM might be of nurse bee age and are foraging precociously. If mites entering on foragers significantly increase Varroa and DWV levels, any advantages that supplemental pollen feeding have on improving immune function or reducing mite reproduction may be negated. However, pollen feeding might provide greater tolerance to Varroa and virus at both the individual and population levels through greater worker longevity and higher brood rearing rates.

Technical Abstract: The effects that feeding supplemental pollen have on Varroa infestation and virus levels were measured in honey bee colonies from July to December. Colonies fed supplemental pollen had significantly larger populations than unfed colonies and had higher survival rates. However, feeding pollen did not affect levels of Varroa infestation or deformed wing virus (DWV). Varroa population growth was correlated with the frequency of foragers with mites (FWM) captured at the colony entrance, and these frequencies were similar between fed and unfed colonies. DWV increased as bees aged and as Varroa populations increased in colonies with or without supplemental pollen feeding. Interestingly, FWM had DWV levels that were similar to those of nurse bees, and significantly lower than foragers without mites. These findings suggest that FWM might be of nurse bee age and are foraging precociously. If mites entering on foragers significantly increase Varroa and DWV levels, any advantages that supplemental pollen feeding have on improving immune function or reducing mite reproduction may be negated. However, pollen feeding might provide greater tolerance to Varroa and virus at both the individual and the population levels through greater worker longevity and higherod rearing rates.