Influence of increased CO2 on mortality of Varroa destructor during the indoor storage of honey bee (Apis mellifera L.) colonies

Primary Author: Stephen Onayemi

Faculty Sponsor: Brandon Hopkins


Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Agricultural and Natural Resource Sciences

Campus: Pullman




Indoor storage of honey bee (Apis mellifera L.) colonies during winter months has been practiced in cold climates for decades. Evidence from a recent study showed that conditions during storage could lead to a decrease in the levels of pathogen prevalence in colonies. Varroa is considered one of the most significant threats to colony health and survival, and as such, it is a major contributor to winter mortality and virus transmission in honey bees. An investigation on the effects of increased CO2 on the mortality of Varroa destructor during indoor storage of honey bees was carried out. Eight-frame single deep colonies (n=16) were held in two environmental chambers (both at 4 C) with one set at 8.5% CO2 while the other at normal atmospheric CO2. Each week during the experiment dead/falling mites were collected from the bottom of each colony and counted. At the end of the 62-day experiment, the surviving colonies were treated with a miticide to collect any remaining mites. Mite mortality was calculated by dividing the number of mites collected weekly by the total number of mites collected for each colony. A significant difference in mite mortality was found in colonies held at 8.5% CO2 (73%) in comparison with colonies held at normal atmospheric CO2 (51%). This study demonstrates that increased CO2 during an indoor storage period could increase mite mortality and in turn, reduce virus transmission and improve honey bee health coming out of the winter months.