Western honeybees, Apis mellifera, serve as important pollinators of crops around the globe. It is estimated that 35% of the world’s crops are dependent on bees for pollination. Globally, they pollinate hundreds of billions of dollars’ worth of crops annually. Without bees for pollination, it is estimated that people would lose one in every three bites of food they eat daily.
Recently, however, there has been concern over honeybee health. Over the past six decades, the number of honey-producing colonies in the U.S. has decreased by half. Part of this decline is due to fewer people keeping bees. But more troubling are the annual losses that beekeepers experience. While beekeepers used to lose less than 20% of their hives annually, they now lose 40% to 60% of their hives annually.
While there is no single cause of these declines and losses, research between the LSU AgCenter and the U.S. Department of Agriculture Honey Bee Breeding, Genetics and Physiology Laboratory in Baton Rouge has aimed to understand how different stressors affect honey bee health. This has involved a two-year study assessing more than 720 colonies that travel across the U.S. providing pollination services.
One of the major stressors that affects honeybee health is the parasitic mite Varroa destructor. This species is cosmopolitan in distribution and has been a major contributor of billions of dollars’ worth of honeybee loss around the globe. This parasitic mite climbs into the cells where baby bees develop (brood cells), where its offspring will feed on the developing pupae. The mite is so large in comparison to its host, it would be the equivalent of a human being attacked by a parasite the size of a basketball. Research continually shows that if colonies are not treated for mites, and mite levels are above a specific threshold, there is a high probability those colonies will not survive the winter. The AgCenter is currently working with the USDA honeybee lab and beekeepers around the state to learn how to best inform beekeepers about mite surveillance and management to improve honeybee health outcomes.
One method to reduce levels of varroa mites has been using honeybees bred with a type of varroa-sensitive hygiene (VSH). VSH bees are able to detect brood cells that contain varroa mites. Once detected, the adult nurse bees will open up infected brood cells and remove those from the colony. In our studies, we were able to compare the long-term health of colonies with a type of VSH bee to colonies with traditional commercial (Italian) honeybees. After two years of data collection, we continually see improved colony survival, fewer mite levels and lower pathogen levels in bees exhibiting this hygienic behavior.
Research between the AgCenter and the USDA honeybee lab has focused on understanding the impact of varroa mites, as well as the pathogens they transmit to honey bees. While honeybees are affected by a multitude of pathogens, one of the most prevalent in nature is known as deformed wing virus (DWV). DWV is transmitted primarily by varroa mites to honeybees. While not all bees will become symptomatic, those that do will emerge as adults with crippled wings, making them unable to fly. Our research projects with the USDA bee lab have enabled us to better understand the epidemiology of this virus. Projects have included comparing virus dissemination and pathogenicity between different types of bees, such as VSH bees and commercial Italian honeybees. The goal has been to understand if genetics influences viral susceptibility. Another way to understand this has been to study how the virus itself influences the queen reproduction and survival. For each colony of tens of thousands of bees, there is only a single queen. Her genetics and health affect much of what goes on in the colony.Therefore, these studies have the potential to better improve pathogen management strategies by understanding how queen genetics may also influence the epidemiology of honeybee pathogens.
Other important stress factors to honeybees are the loss of habitat and lack of available forage. Honeybees convert nectar from flowering plants into honey, which they store for future usage. In addition, they also collect and store pollen as a protein source. Wildflowers, such as clover, provide an excellent source of nutrients for bees, yet resources around the landscape are often limited, which, in turn, affect colony health.
While there is much concern over how the loss of habitat and forage affect honeybees, these stress factors also influence other pollinators as well. In Louisiana alone, we have more than 200 species of native bees that can serve as pollinators. There are also several butterflies, beetles and flies that can also serve as pollinators. The AgCenter has numerous publications on improving pollinator habitat, including information on edible gardening to attract pollinators. In addition, AgCenter researchers are studying better management strategies in pasture habitats to improve pollinator diversity and health.
(This article appears in the spring 2019 issue of Louisiana Agriculture.)
Honeybee. Photo by Phil Stouffer
The Pollinator Garden at the LSU AgCenter Botanic Gardens at Burden is an oasis of nectar- and pollen-rich plants such as milkweed, salvia, hibiscus and others that are attractive to insects and other animals that spread pollen and fertilize flowers and crops. The garden is also a teaching tool designed to educate children and adults alike on the importance of pollinators. Next to the Children’s Garden, the Pollinator Garden features plants that attract pollinators as well as pollinator-themed play equipment that includes a dragonfly seesaw, a honeycomb climbing station and a giant caterpillar crawl-through tube. Butterflies are common in the garden, and host plants attract specific butterflies that deposit their eggs on the leaves. The caterpillars, or larvae, that feed on the leaves eventually pupate and emerge as adult butterflies. Photo by Olivia McClure