How the Varroa Mite Co-Opts Honey Bee Behaviors to Its Own Advantage

Entomology Today    By Entomology Today   May 10, 2017

While the Varroa destructor mite is not a highly mobile insect on its own, it takes advantage of the behaviors of honey bees in managed beekeeping settings to spread. In particular, bee colonies in close proximity to each other and less swarming allow mite populations to grow, according to new research. (Photo credit: Scott Bauer, USDA Agricultural Research Service, Bugwood.org)

As the managed honey bee industry continues to grapple with significant annual colony losses, the Varroa destructor mite is emerging as the leading culprit. And, it turns out, the very nature of modern beekeeping may be giving the parasite the exact conditions it needs to spread nearly beyond control.

In an article published yesterday in Environmental Entomology, researchers argue that the Varroa mite has “co-opted” several honey bee behaviors to its own benefit, allowing it to disperse widely even though the mite itself is not a highly mobile insect. The mite’s ability to hitchhike on wandering bees, the infections it transmits to bees, and the density of colonies in managed beekeeping settings make for a deadly combination.

“Beekeepers need to rethink Varroa control and treat Varroa as a migratory pest,” says Gloria DeGrandi-Hoffman, Ph.D., research leader and location coordinator at the U.S. Department of Agriculture-Agricultural Research Service’s Carl Hayden Bee Research Center in Tucson, Arizona, and lead author of the research.

In the wild, bee colonies tend to survive despite Varroa infestations, and colonies are usually located far enough apart to prevent mites from hitching rides to other colonies on foraging bees. Wild bee colonies’ natural habit of periodically swarming—when the colony grows large enough that a portion of its bees splinter off to create a new colony elsewhere—also serves as a mechanism for thinning out the density of mite infestations and their associated pathogens. In managed honey bee settings, though, these dynamics are disrupted, DeGrandi-Hoffman says. Colonies are kept in close proximity, and swarming is prevented.

DeGrandi-Hoffman, USDA-ARS colleague Henry Graham, and Fabiana Ahumada of AgScience Consulting, conducted an 11-month study of 120 honey bee colonies in one commercial bee operation, comparing those treated with mite-targeting insecticide (miticide) in the spring and fall with those treated only in the fall, and they found no significant difference in the results: more than half of the colonies were lost across the board. This aligns with what has been seen by beekeepers and researchers alike in recent years: Varroa populations continue to grow even after being treated with effective miticides. But why? The answer may be in its dispersal mechanisms.

The researchers also conducted mathematical simulations of Varroa mite population dynamics to examine the effects of both migration of foragers between colonies and swarming. When bees can wander into other colonies—either to “rob” them of their honey or because they’ve simply lost their way—Varroa populations across colonies climb. Likewise, prohibiting colonies from splintering periodically via swarming also leads mite populations to rise.

In the wild, DeGrandi-Hoffman and her colleagues note, driving a colony to collapse is against Varroa mites’ own interest; if the colony dies, the mites die with it. But in commercial beekeeping settings, increasing infestation of a colony activates the dispersal mechanisms the mites need to spread. Weakened foragers are more likely to wander to other colonies, and weakened colonies are more likely to see foragers from healthy colonies visit to rob them of honey. In both cases, mites can hitch a ride from one colony to another.

It all adds up to a critical point for managed honey bee industry. The researchers cite the need for new integrated pest management strategies to treat Varroa destructor as a migratory pest, as well as for further research into the specifics of Varroa dispersal.

“Colony losses in the U.S. are at unsustainable levels for commercial beekeepers. These beekeepers supply colonies for the pollination of crops that represent one-third of U.S. agriculture and are essential components of heart healthy and cancer-prevention diets,” says DeGrandi-Hoffman. “This research provides evidence that the tried and true ways of controlling Varroa are no longer feasible, and that new methods that are designed for control of a migratory pest are required.”

https://entomologytoday.org/2017/05/10/how-the-varroa-mite-co-opts-honey-bee-behaviors-to-its-own-advantage/

Read More:
Are Dispersal Mechanisms Changing the Host–Parasite Relationship and Increasing the Virulence of Varroa destructor (Mesostigmata: Varroidae) in Managed Honey Bee (Hymenoptera: Apidae) Colonies? “Are Dispersal Mechanisms Changing the Host–Parasite Relationship and Increasing the Virulence of Varroa destructor (Mesostigmata: Varroidae) in Managed Honey Bee (Hymenoptera: Apidae) Colonies?”  Environmental Entomology

A Diet To Help Conserve Bees When Food Is Scarce

  Agricultural Research Service (ARS) Posted by Kim Kaplan, Public Affairs Specialist October 6, 2015

MegaBee, an artificial diet developed by ARS and S.A.F.E. R&D, LLC, helps sustain honey bees in the face of pressures such as poor nutrition, pathogens, parasites, and sublethal exposure to pesticides.This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from USDA’s rich science and research portfolio.

The fact that honey bees are a critical link in pollinating plants, especially our crops, has become better known to the public in the past few years. In exchange for their labor, flowers provide bees with pollen and nectar as food. But few people wonder what’s available for bees to eat when there are few plants blooming in the late fall and early winter.

During such times of the year, with little natural food available, honey bee colonies usually fade a little. But this is exactly the time of year when beekeepers want their colonies to be producing lots of healthy, robust bees ready to be trucked to California to plunge into pollinating millions of almond blossoms in February.

Oddly enough, while beekeepers have been feeding their colonies for hundreds of years, we still do not know the exact nutritional components of the perfect bee diet to replace pollen and nectar.

So honey bee expert and research leader Gloria DeGrandi-Hoffman and her colleagues at USDA Agricultural Research Service’s (ARS) Carl Hayden Bee Research Center in Tucson, Arizona, partnered with entomologist Gordon I. Wardell of Tucson-based S.A.F.E. (Sensible Alternatives for the Environment) R&D, LLC, to develop a new and better artificial diet based on scientific data and research into honey bee taste preferences.

That was in 2002. All in all, the team tested nearly a thousand different combinations of proteins and carbohydrates before honey bees gave a formulation their stamp of approval in 2007, and the MegaBee diet came to market. It has been a growing success ever since.

Nectar and pollen from flowers are the bees natural food.Today, researchers have come to recognize the role of poor nutrition in honey bees’ inability to deal with the many stresses they experience such as pathogens, parasites and sublethal exposure to pesticides. Such stresses may include extended periods of time when colonies have access to only a single plant or crop for food. Supplemental feeding with an artificial diet like MegaBee may be one of the keys for beekeepers to help their bees survive extended periods when pollen is in short supply.

See more at: http://blogs.usda.gov/2015/10/06/a-diet-to-help-conserve-bees-when-food-is-scarce/#sthash.f6mG5Gsr.dpuf