Oxford Bees

Varroa Resistance

The value of a feral colony

Submitted by will on Fri, 30/03/2018 - 19:13

People value things more when other people value them. Price is a useful proxy for judging what other people value, but price reflects usefulness and abundance and status and cultural history.

It takes experience and time to learn the value of that which is abundant, cheap or free. It takes no time to be influenced by someone.

I value feral bee colonies. Established feral colonies are where natural selection is allowed to happen. Established feral colonies are survivors.

Bee Keepers in England have valued the Italian strains for decades, particularly those which were selectively bred from 'Italian' stock at Buckfast Abbey: the Buckfast Bee. Professional and mainstream bee keepers value the Buckfast Bee because it is easy to manage and produces lots of honey. It's a product of modern agricultural thinking.

Honey bees now face new challenges: new invasive species; new pests; invigorated diseases; changing land use leading to less forage, or seasonal variability in the amounts of forage; new pesticides.

The Varroa mite is a significant challenge. It is a pest which was in balance with its' original host, the Asian Honey Bee (Apis Cerana). The move to the Western Honey Bee (Apis Mellifera) changed the mite's life-cycle so that it now infests worker brood as well as Drone. This has increased its' virulence. The mite has also super-charged existing viral diseases -- particularly Deformed Wing Virus which is implicated in the increasing number of failing colonies (Colony Collapse Disorder). The Varroa mite is a parasite which is out of balance with its' host, the Western Honey Bee.

The popular Buckfast Bee does not cope well with Varroa.

Feral colonies are probably either descended from, or related to Buckfasts. What sets ferals apart is that they have interbred freely and been subject to natural selection. Newly escaped colonies which cannot cope with the new challenges will die within 2 or 3 seasons. My best survivor colonies have been untreated for at least 5 seasons.

Oxfordshire is unlikely to be the place where Western Honey Bees evolve a resistance to Varroa. Evolution is not that convenient. Oxfordshire can be a place where natural selection is allowed so that the bees can reach a survivable balance with Varroa. My low intervention approach is intended to support that.

Submitted by will on Sun, 15/10/2017 - 20:28

I visited my out-apiary today and examined the removable hive floors for evidence of recent activity.

Three hives (D, F and G) show evidence of recent brood emergence. There were also hundreds of dead mites. Hive D had been especially prolific. There was also crystallised sugar which suggests that old honey is being eaten or cells are being cleaned out.

One hive (C) was so wet with condensation that it was impossible to tell what had fallen to the floor. There must have been wax and pollen. Presumably mites but it was hard to tell. The hive is ventilated but I assume that there has been a strong honey flow and the ventilation has been insufficient.

One Hive (E) was in crisis but activity seems much reduced. Fewer mites and fewer hatchings. This might mean that the crisis has abated or that the colony is in deep trouble.

The overall picture is that foraging is still strong during the warmer parts of the day. Brood rearing is strong which is supporting very high levels of mites. This picture is matched by Hives A and H in Headington. A is dropping lots of mites. Both A and H are bringing in large amounts of pollen. H is building lots of comb (which A doesn't need to do).

The Varroa population models suggest that colonies risk collapse when total mite numbers is greater than 1,000. I would only be confident that hive H has fewer than that.

What happens next? This is where my commitment to no-treatment beekeeping is tested.

Submitted by will on Thu, 25/05/2017 - 19:40

Parasites rely on another organism for aspects of their feeding and/or reproduction. Whilst parasitism is a complex subject, the relationship between Western Honey Bees and Varroa mites is relatively simple. The mites live entirely with and on the bees. Food, reproduction and transport is all provided by bees. In this case, if the host dies so does the parasite.

Some parasites have periods where they are hosted by a different organism - for example Influenza or Malaria. Some parasites have long lived dormant phases - for example Anthrax. These can fatally damage their hosts without killing themselves. Anthrax depends on killing its' host so that decay releases it from the body cavity. Varroa is not like this.

Until recently I have been looking for an increase in the tolerance or resistance of bees to Varroa and its' diseases. I now see that the virulence of the mite should also decrease. This will bring the relationship into a balance where the parasite will not kill itself by killing its' host.

The Varroa mite became much more virulent when they crossed to the Western Honey Bee (Apis Mellifera) from the Eastern Honey Bee (Apis Cerana). It started to infect worker brood, rather than just drone brood. This gave it many more opportunities to reproduce and so overwhelm colonies. I don't expect the Varroa to stop infecting worker brood, but I do expect some change in the rate of reproduction or the effectiveness of viral infection.

My untreated hives have survived for extended periods without suffering Colony Collapse Disorder. Maybe collapsing colonies are subject to multiple stresses: Varroa plus intensive apiculture and/or another disease. I don't see evidence of resistance but I do see tolerance and patterns of disease expression which don't have significant effects on the colony.

Submitted by will on Sun, 12/03/2017 - 14:55

Colonies can fail over winter. Surveys suggest that about 10% fail in a good year; more in a bad one. At the moment, none of my colonies have failed. I'm happy.

It's too early to be certain that all will survive into summer. Each colony will strike a balance between brood production and foraging. If they make too much brood when the forage is poor, they may starve.

Failure can happen because of disease, starvation or an external event. There are lots of diseases and lots of events. There is only one cause of starvation.

My big event this year (the knock-down during Storm Doris) could have been fatal for the two hives if they hadn't been secured with hive straps. The exposure caused by an unsealed hive would have chilled and killed some of the bees; brood might have died from exposure and consumption of stores would have risen[1]. Instead the damage seems to have been slight. The hives toppled so that the frames were end on (rather than face on). The hive body stayed together. I arrived soon after the event.

Disease does not seem to have adversely affected them. There is Varroa in all five colonies. Four of these are untreated, but were only established last year. One was treated in Spring last year before I resolved to stop. It's too early to be certain that all have become Varroa tolerant but I have reason to hope. There are signs of CBPV and a worrying pile of rotted bee bodies outside Hive D. We'll see how that hive fares.

Even the late swarm in Hive E seems to be ok. I'm optimistic coming into 2017.

[1]: An article published by Thorne in Nov 2016 suggested that weekly consumption of stores by a colony would double if they are disturbed.

Submitted by will on Wed, 10/08/2016 - 06:50

Host parasite relationships can end in one of only three ways: extinction for either or in a balance between the two. The most likely outcome is surely to find a balance.

Varroa Destructor is an introduced pest to the Western Honey Bee (Apis Mellifera). The bee does not have strongly expressed resistance to mite. The most advantageous position for the mite is to be in balance with its host. Varroa rely entirely on the Honey Bee for their complete lifecycle. There's no point in exterminating yourself by killing your host. When will that resistance emerge? There are reports that it is starting around Oxfordshire already.

Honey Bee resistance could emerge through hygienic behaviours include grooming or removal of infected brood, or through immunity to the diseases which the mite carries and exacerbates. I don't know of any other ways, but there may be more.

In Swindon, a local beekeeper reports that his bees are ejecting infected brood and biting mites. None of my hives have collapsed, despite strongly expressed Varoosis diseases early in the season (DWV and at least one of the paralysing viruses). Evidence of those diseases stopped after May this year. Mite fall in Hive A had been alarmingly high. The fall of mites was much lower over summer, but that's probably due to them being within brood. It will be interesting to see whether mite fall rises into the Autumn.

I will comment on my own hives and pass on any credible reports of resistance in my area.