Varroa mite, Varroa destructor, Laelapidae

Found worldwide, the varroa mite is an external parasitic mite that attacks and feeds on honey bees and is one of the most damaging honey bee pests in the world. A significant mite infestation leads to the death of a honey bee colony.

The mites have flattened, curved bodies that allow them to attach to adult bees between the abdominal segments, though they will also feed on larvae. They feed primarily on honey bee fat body tissue and not hemolymph, weakening the bee and potentially acting as a vector for harmful viruses.

Varroa destructor, the leading cause of beekeeper angst.  

Researchers at the University of Sydney have found that the relationship between the tissue-sucking Varroa mite and virulence of a virus of honey bees, has most likely been misunderstood.

The study challenges the long-held belief that the parasitic Varroa mite—a mite that sucks the tissue of honey bees—transmits the Deformed Wing Virus of honeybees and in doing so changes the virus to make it more virulent and deadly.

Research published today in Proceedings of The Royal Society B: Biological Sciences concludes that this belief is incorrect.

"The prevailing wisdom is that the mite selects for very virulent strains of the virus," said Professor Madeleine Beekman from the School of Life and Environmental Sciences at the University of Sydney.

"For that reason, the virus is now known as a very dangerous virus and the Australian beekeepers are adamant this virus should not get into the country. In fact, there is legislation that prevents the import of any bee products that could contain the virus. But our work shows that the virus is more likely to be an innocent bystander."

Australia is the only country in the world to remain free of the Varroa mite. This makes Australian honey and wax valuable because it is free of chemical residues used to eliminate the parasite.

"Australia is the last country on the planet to produce completely pure honey," says Professor Beekman. "But the mite is highly likely to arrive in Australia on shipping containers so we need to understand how the mite and the virus interact."

…farmed bees is a sign of trouble for wild bees too Bret Adee is one of the largest beekeepers in the US, with 2 billion bees across 55,000 hives. The business has been in his family since the 1930s, and sends truckloads of bees across the country from South Dakota, pollinating crops such as almonds, onions, watermelons and cucumbers. Last December, his bees were wintering in California when the weather turned cold. Bees grouped on top of hives trying to keep warm. “Every time I went out to the beehive there were less and less,” says Adee. “Then a week later, there’d be more dead ones to pick up … every week there is attrition, just continually going down.” Adee went on to lose 75% of his bees. “It’s almost depressingly sad,” he says. “If we have a similar situation this year – I sure hope we don’t – then we’re in a death spiral.” It developed into the largest US honeybee die-off on record, with beekeepers losing on average 60% of their colonies, at a cost of $600m (£440m). Scientists have been scrambling to discover what happened; now the culprits are emerging. A research paper published by the US Department of Agriculture (USDA), though not yet peer-reviewed, has found nearly all colonies had contracted a bee virus spread by parasitic mites that appear to have developed resistance to the main chemicals used to control them. Varroa mites – equivalent in size to a dinner plate on a human body – crawl and jump between worker bees. If there are no infections present, they do not typically damage the bee. But if diseases are present, they quickly spread them.

New Post has been published on https://www.beekeepingfiji.com/?p=4098

Varroa - Part 2 : Controlling Varroa Mites

Papua New Guinean beekeepers have suffered from the same species of varroa 10 years longer than Fijians, so we can learn from the PNG experience.

Anecdotal evidence from PNG suggests substantial negative impacts on honey production. In the early years, untreated in PNG, it caused bee colony deaths estimated at 60% – 90% in some areas.

One study reported disease consistent with parasitic mite syndrome. However, many bee colonies survived and show some tolerance to the mites.

Integrated pest management (IPM) approach

Most varroa mite experts advise beekeepers to adopt an integrated pest management (IPM) approach to controlling varroa.

An IPM approach uses several methods to reduce the adverse effects of mites.

The different methods of controlling mites have serious trade-offs on effectiveness, cost and labor requirements.

Here are a few ways:

Method 1 of Controlling Varroa Mites: Mechanical And Cultural (Non-Chemical) Control

Removing drone brood is probably the most practical non-chemical varroa mite control method for Fiji, as it only takes a minute to cut drone brood out of frames in the top box of a hive during regular monthly inspections. It can be effective because varroa reproduces primarily on drone pupae.

Varroa mites show a strong preference for breeding in drone cells because they can raise more babies during the drone’s longer development period.

Carve drone brood out of specially designed frames

Some beekeepers overseas routinely carve drone brood out of specially designed frames for this purpose. It is also a good beekeeping practice to keep newer, good quality worker-sized comb in the bottom hive box, so drone pupae only needs to be removed from the top box.

I made some of these frames and plan to place two into the top box of each hive. The bees will build mostly drone-comb in the open bottom section.

A shallow frame in a full-depth box allows the bees to build comb on the bottom of the frame. Most of the cells the bees build will be drone-sized. BTW, the light patches on the comb are only caused by sunlight

Photos courtesy of John Caldeira

Causing a ‘break’ in bee brood-rearing

Causing a ‘break’ in bee brood-rearing is another control method, as it denies the mites a place to breed.

The easiest way to do this is to create walk-away splits each year as they are broodless for the first few weeks. Pinching old queens to let colonies raise a new one works in a similar way.

Caging queens for a couple of weeks to stop egg-laying also works, but that would be an enormous amount of labour for someone with many hives.

Hive bottoms with screens

Hive bottoms with screens that allow mites to fall through instead of solid wood is commonly believed to reduce mite loads by approximately 10%, as some mites naturally fall to the bottom and cannot return to the colony.

A screened bottom board allows mites and debris to fall through, reducing the mite load. Unfortunately, the right size mesh (approx 3mm holes) is nearly impossible to find in Fiji. Has anyone found a good substitute? Photos courtesy of John Caldeira

The screening must be large enough for the mites to fall through, but small enough to keep out robber bees and other pests.

The best screening to use has 3 mm holes, commonly referred to as “number 8 mesh” (8 wires to the inch) but it has been difficult to find this mesh in Fiji.

This same mesh is good for the lids on sugar-shake jars.

Arranging hives in an apiary so that hive entrances are not near each other will minimize the ‘drifting’ of forager bees that mistakenly enter the wrong hive, thus reducing the spread of varroa between hives.

Photos courtesy of John Caldeira.