Application of carbon dioxide for monitoring for varroa destructor infestation yields inaccurate results

Authors: Rinkevich Jr, Frank

Submitted to: Journal of Apicultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Varroa destructor is the major cause of honey bee colony losses. It is important to monitor Varroa infestation to make treatment decisions as well as predicting if the colony will be lost with high Varroa infestation. Many methods exist to monitor for Varroa and vary significantly in their cost, time, accuracy, expertise required, and equipment needed. A new method that uses CO2 to temporarily knock out bees so Varroa falls off them them would allow for rapid and non lethal method for Varroa monitoring. The data shown here indicate that using CO2 to monitor for Varroa yields very unreliable results that dramatically underestimate the true Varroa infestation level thus leading to missed treatment opportunities as well as enhancing potential colony losses.

Technical Abstract: The parasitic mite Varroa destructor is responsible for the decimation of a significant proportion of honey bee colonies around the world through their traumatic feeding behavior and their efficiency to vector many honey bee viruses. The negative impact of Varroa on honey bee colonies cannot be understated. Monitoring Varroa infestation levels is fundamental to a successful Varroa management program with the goal of reduced colony losses. Many methods exist to monitor Varroa infestation with varying degrees of usability, cost in time, labor, and equipment, and accuracy. Injection of CO2 to anesthetize bees and dislodge Varroa is attractive because it would yield rapid results without having to sacrifices bees. This research shows that using CO2 for Varroa monitoring administered using either a CO2 cartridge gun or by a lab tank is highly ineffective and yields very low estimates of Varroa infestation, thus undermining any basis for a successful Varroa monitoring and management program. Washing bees with soapy water or alcohol remains the standard for rapid, low cost, and relatively accurate Varroa infestation monitoring.