The identification of miticide resistance in Varroa mites and the development of novel Varroa control strategies for improving honey bee health

Since its introduction into the United States almost three decades ago, the Varroa mite (Varroa destructor) has arguably been the most destructive pest of the honey bee (Apis mellifera). In order to control Varroa populations, beekeepers commonly apply miticides in the hive. However, beekeepers have observed widespread Varroa resistance to the miticides. The most commonly used miticides, and often the most frequently detected miticides in the colony, are coumaphos (Checkmite+), fluvalinate (Apistan), and amitraz (Apivar). Our aim of this study is to characterize miticide resistance in Varroa in the Southeast United States and identify novel strategies for improving our control of Varroa. Honey bees were collected from ten locations throughout Florida and Georgia. The bees were transported to the laboratory and treated with coumaphos, fluvalinate, or amitraz for three days. Mite mortality was recorded daily and surviving mites for each treatment were collected and quantified at the end of the three days. Data were analyzed to characterize the level of Varroa resistance to each of the miticides according to geographic location. Additionally, we found individual Varroa mites within a single colony to be differentially susceptible to coumaphos, fluvalinate, and amitraz. Over a period of three days, colonies were treated with a rotation of miticides (eg. amitraz day 1, coumaphos day 2, and fluvalinate day 3) to characterize Varroa susceptibility within each colony and determine if miticide rotation is an advantageous Varroa control strategy and potentially reduce the development of miticide resistance. Ongoing research in our laboratory aims to identify genes in Varroa that may be responsible for miticide resistance. By identifying these genes, we can increase the susceptibility of Varroa to chemical control by silencing these detoxification genes, therefore reducing our long-term dependence on miticide use within the colony.