Varroa mite removal from whole honey bee colonies by powdered sugar dusting is enhanced by crowding and mechanical agitation of treated workers

Authors: Carroll, Mark; Brown, Nicholas

Submitted to: Journal of Apicultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2024
Publication Date: 6/18/2024
Citation: Carroll, M.J., Brown, N.J. 2024. Varroa mite removal from whole honey bee colonies by powdered sugar dusting is enhanced by crowding and mechanical agitation of treated workers. Journal of Apicultural Research. 1-11. https://doi.org/10.1080/00218839.2024.2361959.
DOI: https://doi.org/10.1080/00218839.2024.2361959

Interpretive Summary: The honey bee parasite Varroa mite is the most destructive parasite of honey bees. New control treatments are needed since Varroa mites have developed resistance to conventional miticides currently used to protect honey bee colonies. Varroa mites are susceptible to removal by dusting agents that physically interfere with its ability to cling to its phoretic hosts. Here we describe modifications to established powdered sugar dusting techniques that increased mite drop (death) and allow for greater mite removal from whole colonies. These new methods increase body-to-body contact and rubbing of workers through crowding and mechanical agitation to supplement mite removal through autogrooming. Adult workers were isolated in a screened sugar shake box out the colony, dusted with powdered sugar, then carefully shaken and bounced in crowded piles for one minute. Worker crowding combined with powdered sugar dusting and sustained worker contact resulted in an average removal of 92% of phoretic mites over three successive weekly mite treatments. These composite methods provided effective mite control comparable to the miticide Apiguard (thymol) without discernable negative effects on colonies. Four months after treatment, powdered sugar shake-treated colonies had adult and brood populations at similar levels as colonies treated with Apiguard and at higher levels than untreated control colonies. Colonies also maintained queens and reared similar numbers of queen cells across treatments. Further comparisons of method components revealed that mechanical agitation of bunched workers enhanced mite drop due to powdered sugar dusting. Mechanical agitation on its own did not result in mite drop; however, mite drop due to powdered sugar dusting increased with box shaking. This method provides a rapid if laborious technique for reducing mite populations without chemical residues from restricted miticides.

Technical Abstract: The honey bee parasite Varroa mite is the most destructive parasite of honey bees. New control treatments are needed since Varroa mites have developed resistance to conventional miticide treatments currently used to protect honey bee colonies. Varroa mites are susceptible to removal by dusting agents that physically interfere with its ability to cling to its phoretic hosts. Here we describe modifications to established powdered sugar dusting techniques that increased mite drop (death) and allow for greater mite removal from whole colonies. These new methods increase body-to-body contact and rubbing of workers through crowding and mechanical agitation to supplement mite removal through autogrooming. Adult workers were isolated in a screened sugar shake box out the colony, dusted with powdered sugar, then carefully shaken and bounced in crowded piles for one minute. Worker crowding combined with powdered sugar dusting and sustained worker contact resulted in an average removal of 92% of phoretic mites over three successive weekly mite treatments. These composite methods provided effective mite control comparable to the miticide Apiguard (thymol) without discernable negative effects on colonies. Four months after treatment, powdered sugar shake-treated colonies had adult and brood populations at similar levels as colonies treated with Apiguard and at higher levels than untreated control colonies. Colonies also maintained queens and reared similar numbers of queen cells across treatments. Further comparisons of method components revealed that mechanical agitation of bunched workers enhanced mite drop due to powdered sugar dusting. Mechanical agitation on its own did not result in mite drop; however, mite drop due to powdered sugar dusting increased with box shaking. This method provides a rapid if laborious technique for reducing mite populations without chemical residues from restricted miticides.