Selective breeding protects honey bees from the Varroa mite in the long term

Beekeepers transport colonies to support large-scale farming. Recorded in South Dakota. Credit: Thomas O’Shea-Wheller

A new breed of honey bee marks a major advance in the global fight against the parasite Varroa mite, new research shows.

The invasive mite, which has spread to every continent except Australia and Antarctica, has been the main threat to honey Bees since they first spread 50 years ago.

In the study — by the Universities of Louisiana and Exeter and the United States Department of Agriculture’s (USDA) Agricultural Research Service — “pol-line” bees bred for resistance to the mite in a rigorous 20-year breeding program were alongside one Standard variety tested in a large-scale pollination farm.

The mite-resistant bees were more than twice as likely to survive the winter (60% survival versus 26% for standard honey bees). While the standard honey bees suffered high losses unless extensive chemical miticide treatments were applied.

“That Varroa Mite is the biggest threat to managed bee colonies worldwide,” said Dr Thomas O’Shea-Wheller of the Environment and Sustainability Institute at the Penryn Campus in Exeter, Cornwall.

“So far, new methods of controlling the mites – and the diseases they carry – have had limited success, and the mites are becoming increasingly resistant to chemical treatments. It’s a ticking time bomb.

“By selectively breeding bees that identify mites and remove them from their colonies, our study found a significant reduction in mite numbers, and most importantly, a doubling of numbers colony Survive.

“Although this is the first large-scale trial, continued breeding and use of these bees has consistently shown promising results.

“This type of resistance offers a natural and sustainable solution to the threat of Varroa mites, and does not rely on chemicals or human intervention.”

The study was conducted in three US states (Mississippi, California and North Dakota) where commercial beekeepers relocate tens of thousands of colonies annually to provide pollination for large-scale agriculture.

Varroa Mites originated in Asia, so European honey bees (most common species kept for pollination) have not co-evolved with them and therefore do not have effective resistance.

Selective breeding protects honey bees from the Varroa mite in the long term

Bees in California. Credit: Thomas O’Shea-Wheller

Like humans, managed bees are largely “decoupled”. natural selectionsaid dr O’Shea-Wheller, so they cannot develop resistance like they might in the wild.

However, managed bees sometimes respond to mites (which reproduce in the cells of bee larvae) by expelling infested larvae – killing both the larvae and the mites, in a behavior known as Varroa-sensitive hygiene (VSH).

Selective breeding for this trait can produce colonies that automatically protect themselves from infestation while maintaining large colony sizes and copious honey production.

“What’s great about this particular trait is that we’ve learned that honeybees of all species express it at some level, so we know that with the right tools, it can be nurtured and selected in all bees,” said research molecular biologist Dr. Michael Simone-Finstrom of the USDA Agricultural Research Service.

The survival of the colonies over the winter is particularly important for beekeepers, because honey bees are in high demand in winter early spring– a key time for pollination of high-value crops such as almonds.

The study also looked at associated virus levels Varroa mites in bee colonies.

The colonies bred for Varroa Resistance showed lower levels of three major viruses (DWV-A, DWV-B and CBPV).

Interestingly, however, when examined separately by mite infestation levels, these viruses were not strong predictors of colony losses.

“A lot of the research is focused on the viruses, perhaps not enough focus on the mites,” said Dr. O’Shea-Wheller.

“The viruses are clearly important, but we have to step back and be rigorous to get the best practical results, because if you control the mites, you automatically control the viruses they transmit.”

dr O’Shea-Wheller said beekeeping and testing is expensive and time-consuming, but this breeding mite-resistant bees is cost effective in the long term and may be the only sustainable solution to deal with it Varroa Pandemic.

The paper published in the journal Scientific Reportsis entitled: “A stock obtained from honey bees confers resistance to Varroa Destructor and associated viral transmission.”


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More information:
A honey bee-derived stock confers resistance to Varroa destructor and associated virus transmission.”, Scientific Reports (2022). DOI: 10.1038/s41598-022-08643-w

Citation: Selective Breeding Sustainably Protects Honey Bees from Varroa Mite (2022 April 7) Retrieved April 8, 2022 from https://phys.org/news/2022-04-sustainably-honey-bees-varroa-mite.html

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