Selective breeding sustainably protects honey bees from Varroa mite —


A brand new breed of honey bees offers a serious advance within the world battle towards the parasitic Varroa mite, new analysis reveals.

The invasive mite, which has unfold to all continents besides Australia and Antarctica, has been the prime menace to honey bees since its preliminary growth 50 years in the past.

Within the examine — by the colleges of Louisiana and Exeter, and the Agricultural Analysis Service of the US Division of Agriculture (USDA) — “Pol-line” bees, bred for resistance to the mite in a rigorous 20-year breeding programme, had been trialled alongside a typical selection in a large-scale pollination operation.

The mite-resistant bees had been greater than twice as prone to survive the winter (60% survival in comparison with 26% in customary honey bees). Whereas the usual honey bees skilled excessive losses until intensive chemical miticide remedies had been used.

“The Varroa mite is the best menace to managed honey bee colonies globally,” mentioned Dr Thomas O’Shea-Wheller, of the Surroundings and Sustainability Institute at Exeter’s Penryn Campus in Cornwall.

“Thus far, new strategies to regulate the mites — and the illnesses that they carry — have had restricted success, and the mites have gotten more and more immune to chemical remedies. It is a ticking time-bomb.

“By selectively breeding bees that establish and take away mites from their colonies, our examine discovered a major discount in mite numbers, and crucially, a two-fold enhance in colony survival.

“Whereas that is the primary large-scale trial, continued breeding and use of those bees has proven constantly promising outcomes.

“This type of resistance offers a pure and sustainable answer to the menace posed by Varroa mites, and doesn’t depend on chemical compounds or human intervention.”

The examine happened throughout three US states (Mississippi, California, and North Dakota), the place business beekeepers transfer tens of 1000’s of colonies yearly to supply pollination for large-scale agriculture.

Varroa mites originated in Asia, so European honey bees (the most typical species stored for pollination) haven’t advanced alongside them, and due to this fact lack efficient resistance.

Like people, managed bees are largely “decoupled” from pure choice, Dr O’Shea-Wheller mentioned, so they can’t develop resistance like they may within the wild.

Nevertheless, managed bees generally reply to mites (which reproduce within the cells of bee larvae) by expelling infested larvae — killing each the larvae and the mites, in a behaviour generally known as Varroa-sensitive hygiene (VSH).

By selectively breeding for this trait, colonies could be produced that robotically defend themselves from infestation, whereas sustaining giant colony sizes and ample honey manufacturing.

“The wonderful thing about this explicit trait is that we have realized honey bees of every type categorical it at some stage, so we all know that with the suitable instruments, it may be promoted and chosen for in everybody’s bees,” mentioned analysis molecular biologist Dr Michael Simone-Finstrom, of the USDA Agricultural Analysis Service.

Colony survival over the winter is especially essential for beekeepers, as a result of honey bees are in excessive demand within the early spring — a key time for pollinating high-value crops equivalent to almonds.

The examine additionally examined ranges of viruses related to Varroa mites in bee colonies.

The colonies bred for Varroa resistance confirmed decrease ranges of three main viruses (DWV-A, DWV-B, and CBPV).

Apparently nonetheless, when examined individually from ranges of mite infestation, these viruses weren’t robust predictors of colony losses.

“Loads of analysis is focussed on the viruses, with maybe not sufficient concentrate on the mites themselves,” Dr O’Shea-Wheller mentioned.

“The viruses are clearly essential, however we have to take a step again and be rigorous in delivering one of the best sensible outcomes, as a result of for those who management the mites, you robotically management for the viruses that they transmit.”

Dr O’Shea-Wheller mentioned bee breeding and testing is dear and takes time, however that breeding mite-resistant bees is cost-effective in the long run, and is prone to be the one sustainable answer to take care of the Varroa pandemic.

The examine was funded by USDA.