A comparison of Varroa destructor (Acari: Varroidae) collection methods and survivability in in vitro rearing systems

Authors: NOBLE, NOBLE - University Of Florida; Stuhl, Charles; NESBIT, MILES - University Of Florida; WOODS, RACHEL - University Of Florida; ELLIS, JAMES - University Of Florida

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2020
Publication Date: 3/31/2021
Citation: Noble, N.; Stuhl, C.J.; Nesbit, M.; Woods, R.; Ellis, J. 2021. A comparison of Varroa destructor (Acari: Varroidae) collection methods and survivability in in vitro rearing systems. Florida Entomologist. 104:13-17. https://doi.org/10.1653/024.104.0103.
DOI: https://doi.org/10.1653/024.104.0103

Interpretive Summary: The varroa mite, Varroa destructor is a serious threat to the Western and European honey bee, Apis mellifera L. Honey bees are crucial in their role as pollinators for agricultural crops in the United States and adds more than $15 billion in value to agricultural crops each year. Pollinators provide a foundation to ensure our diets are plentiful with fruits, nuts, and vegetables. Approximately one third of our food crops rely on honey bees for pollination; thus, honey bees are critical to our Nation’s economy, food security, and environmental health. Unfortunately, the honey bee population has been in decline over the past decade due to the varroa mite, which has a major impact on pollinator health in North America and other parts of the world. The varroa mite is an external parasite that transmits many honey bee viruses. USDA-ARS scientists at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL compared two wild varroa mite collection techniques – one that uses carbon dioxide (CO2), and the other that utilizes a combination of powdered sugar and vigorous shaking dislodge the mites from the bee known and known as a “sugar shake”. This study evaluated these varroa mite collection techniques to determine how long the mites survived over a period of seven days. Results indicated that mites collected from the sugar shake technique lived significantly longer with only 20% death, while those collected by using the CO2 method lived on average of 3.94 d with 62% dying by day six, and 100% death at day seven. The CO2 exposure was harmful to varroa recovery but did not negatively affect the honey bee. Results from this study will provide the necessary foundational research for continued studies for control of varroa mites while protecting their host, the honeybee.

Technical Abstract: Varroa destructor is an ectoparasites of the Western and European honey bee Apis mellifera. Varroa is a major factor effecting honey bee colony health throughout the world. The ability to access all life stages of the mite in a laboratory requires in vitro mite rearing. This is a crucial step for the advancement in research studies and the development management protocols. Current practices require that laboratory specimens are collected from the wild populations. Traditional collection techniques for obtaining wild phoretic mites has been done using carbon dioxide (CO2) or a method in which a combination of powdered sugar and vigorous shaking dislodge the mites from the bee know as a sugar shake. This study compared two varroa mite collection techniques and measured mortality over time. Collected mites were studied utilizing the ‘varroa maintenance system’ (VMS); a tool for maintaining in vitro populations of varroa on its natural host. This method was used to investigate varroa mortality over time. Our results indicated that mites were collected from the sugar shake lived significantly longer (T= 34.58, df=1, p<0.0001, n= 240), with 20% mortality, while those collected by using the CO2 method live on average of 3.94 d with 62% mortality. CO2 exposure was detrimental to varroa recovery, but not that of the honey bee. The aim of this research was to determine if there was a quantitative difference in survival rates between the CO2 and the sugar shake collection methods. Results from this study will provide information critical in varroa collection for future research. We will further investigate the effects of on CO2 Varro as a possible control measure.