Optimizing Beekeepers’ Strategies for Varroa destructor Management

Abstract

We benefit from a longstanding relationship with the Western honey bee, Apis mellifera. In particular, honey bee pollination is important for crops worldwide. Colony losses are elevated in regions including North America, and long-term monitoring efforts can clarify the situation. One contributor to colony loss is the invasive mite Varroa destructor (“Varroa”) which parasitizes adult and developing bees. While Varroa is predominantly controlled with synthetic miticides, for sustainable management we should integrate multiple techniques into IPM approaches (including natural miticides and cultural control). This will reduce Varroa damage and contribute to long-term sustainable beekeeping. In this dissertation, I conducted studies to describe and improve honey bee health. One study, in collaboration with the Bee Informed Partnership, monitored losses of honey bee colonies across the United States. I found beekeepers periodically lose high numbers of colonies (as much as 50.8% in a year), and they consider Varroa a leading causes of loss. To investigate alternatives to synthetic miticides alone, I tested a combination of registered miticides in fall. It provided rapid control of Varroa but damaged adult bee populations: Treatment combinations are a promising avenue, but more research is needed. In another study, I took advantage of a springtime treatment opportunity to test natural miticides. Two natural treatments provided excellent control of Varroa, showed no damage to colonies and were labor-efficient. Finally, a trial of a slow-release oxalic acid formulation showed its potential as a summer treatment under U.S. beekeeping conditions. While it was not a curative treatment, it limited the growth of Varroa infestations, so may be beneficial as a supplemental treatment in U.S. conditions. In all, these studies highlight the continued pressures on honey bees, and help optimize IPM tools to control Varroa, a key stressor.