Can supplementary pollen feeding reduce varroa mite and virus levels and improve honey bee colony survival?
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Can supplementary pollen feeding reduce varroa mite and virus levels and improve honey bee colony survival? Gloria DeGrandi‑Hoffman1 · Vanessa Corby‑Harris1 · Yanping Chen2 · Henry Graham1 · Mona Chambers1 · Emily Watkins deJong1 · Nicholas Ziolkowski1 · Yun Kang3 · Stephanie Gage1 · Megan Deeter4 · Michael Simone‑Finstrom5 · Lilia de Guzman5 Received: 13 May 2020 / Accepted: 17 October 2020 © The Author(s) 2020
Abstract Varroa destructor is an ectoparasitic mite of immature and adult honey bees that can transmit several single-stranded RNA viruses to its host. Varroa reproduce in brood cells, and mite populations increase as colonies produce brood in spring and summer. Mite numbers also can sharply rise, particularly in the fall, by the migration of varroa into hives on foragers. Colonies with high levels of varroa and viruses often die over the winter. Feeding colonies pollen might keep virus levels low and improve survival because of the positive effects of pollen on immunity and colony growth. We compared varroa and virus levels and overwinter survival in colonies with (fed) and without (unfed) supplemental pollen. We also measured the frequency of capturing foragers with mites (FWM) at colony entrances to determine its relationship to varroa and virus levels. Colonies fed supplemental pollen were larger than unfed colonies and survived longer. Varroa populations and levels of Deformed wing virus (DWV) rose throughout the season, and were similar between fed and unfed colonies. The growth of varroa populations was correlated with FWM in fed and unfed colonies, and significantly affected DWV levels. Increasing frequencies of FWM and the effects on varroa populations might reduce the positive influence of supplemental pollen on immune function. However, pollen feeding can stimulate colony growth and this can improve colony survival. Keywords Overwinter survival · Varroa migration · Tolerance · Resistance
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1049 3-020-00562-7) contains supplementary material, which is available to authorized users. * Gloria DeGrandi‑Hoffman [email protected] 1
USDA-ARS, Tucson, AZ, USA
2
USDA-ARS, Beltsville, MD, USA
3
Arizona State University, Tempe, AZ, USA
4
University of Arizona, Tucson, AZ, USA
5
USDA-ARS, Baton Rouge, LA, USA
13
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Experimental and Applied Acarology
Introduction Parasitic mites are a common vehicle for pathogen transmission in plants and animals enabling diseases to spread to new individuals and persist in host communities (see examples in Combes 2005). A parasitic mite that transmits pathogenic viruses in honey bee colonies is Varroa destructor Anderson and Trueman. Varroa is an ectoparasite of larval and adult honey bees that transmits and activates several single-stranded RNA viruses (Acute bee paralysis virus, ABPV; Black queen cell virus, BQCV; Israeli acute paralysis virus, IAPV; Kashmir bee virus, KBV, Sacbrood bee virus, SBV and Deformed wing virus, DWV) (Chen an
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