Oxford Bees

Varroa Count

No drama from my city hives

Submitted by will on Tue, 14/08/2018 - 16:51

There is very little to report from my hives in Oxford. They're bringing in pollen; there are Drones leaving and returning; there are very few Varroa falling onto the base board*; there are lots of wasps but none getting into the hives.

It's all very calm.

* maybe a dozen between the 4 hives

Varroa drop not quite zero

Submitted by will on Wed, 13/06/2018 - 07:18

Colony 13 is dropping Varroa. They are also cleaning out old comb so there is a lot of debris on the hive floor. I found 2 or maybe 3 Varroa bodies.

This colony is new to my apiary, having been established elsewhere. I haven't really included it in my Varroa Zero post because it's new. Hives D and G are included. There were no Varroa on the floor of either this morning. There doesn't appear to much activity in Hive D at all. I shall have to check them.

Varroa drop zero

Submitted by will on Tue, 12/06/2018 - 05:50

I regularly examine the floors of my hives. The stuff which falls out of the hive tells a story about what the bees are doing. I always look for Varroa mites. I've found none on the floors of any of my hives for several weeks. I don't know why.

Mites on the hive floor can indicate how many mites are living in the colony. Varroa live for between 27 days to about 5 months (source: Managing Varroa, National Bee Unit, 2017). The mites require bee brood to reproduce so it's not surprising that there are fewer mites in the early part of the year. What is surprising is that I'm finding no dead Varroa at all in well established and very active hives.

We had difficult weather in spring. The temperature started to warm and then fell dramatically. This led to a number of colonies dying of complete starvation or isolation starvation. Dead colonies don't support Varroa. Live colonies do, but only in cells with brood. I wonder whether this has interrupted the mite life-cycle and knocked them back. I do not expect to find any colonies where Varroa are entirely absent.

I have 6 occupied hives. Three of these are new colonies. I expect to have lower drop anyway because they arrive only with those Varroa which cling on to swarming bees (during the phoretic part of mite life cycle). I have one established hive where there is an Ant infestation. It's possible that the Ants are taking away the mite bodies. That leaves two established colonies which have brood but are dropping no mites. That's a small number of hives, but striking anyway.

There will be more to say about this later.

7 Hives at the end of the season

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.

Mite Crisis in Hive E

Submitted by will on Tue, 12/09/2017 - 23:01

Hive E is having a Varroa mite crisis. I checked today and for the previous 2 weeks. Each time I found hundreds of dead Varroa mites.

High mite drop can be a factor in colony collapse. I don't expect them to perform well next season - if they survive through the winter. I expect them to be weakened, and any brood raised in early spring will be heavily infected with Deformed Wing Virus or other diseases symptomatic of Varroosis.

I had hoped that the colony would be better able to manage Varroa. They've been untreated for a significant period of time. The swarm came last season from a feral hive in Barton.

Earlier this season they were very bad tempered which may be related. I should have checked whether they were Queen-Right (you bang the side of the hive. If the roar calms down quickly then they have a Queen. If not then they may be in distress and Queen-less).

I doubt whether replacing their Queen this year would have led to this situation. Even if she had no mite tolerance there would have been a time lag to produce vulnerable brood, and then a further lag to build up mite numbers. It seems more likely that this is the difference between mite resistant and mite tolerant. In the former there are hygenic behaviours or adaptations which inhibit Varroa mite reproduction. In the latter the bees just tough it out. I suspect that Hive E is only tolerant. We'll see whether it is tolerant enough.

Hive H showing very low Varroa drop

Submitted by will on Sun, 09/07/2017 - 19:44

I moved Hive H from my garden to my out-apiary on Friday 30th June. I looked at the removable floor today and found 1 Varroa mite. Just 1 in 8 days. Compare that to Hive H which was dropping 20 per day as a new swarm.

The colony in Hive H has been feral for some time. The colony in Hive F had been a standard bought Buckfast queen 2 or 3 years ago. It's possible that the feral colony is adapting to Varroa and has managed to limit its' numbers. The mite is still present - it's endemic and won't now go away.

I'll see how Hive H fares as it settles in.

Hive F still shedding lots of Varroa

Submitted by will on Thu, 11/05/2017 - 05:53

I looked at Hive F's removable floor again on Tuesday 9th May. I counted 24 Varroa mites which had fallen out of the colony. That's 8 per day. Will they survive?

UPDATE: I visited the hive on 12th May after dark. There were another 32 mites. I've counted 88 mites in 7.5 days, an average of about 12 per day. That's very high. This colony has been untreated for a couple of years but it was from a bought queen before that. I don't think much of its' ability to manage Varroa.

Hive F settling in and shedding lots of Varroa

Submitted by will on Sat, 06/05/2017 - 12:37

I put the a swarm from Helen into Hive F on the evening of 2nd May. I had a look at the entrance and the removable hive floor this morning.

The colony appears to be settling in well, despite the colder May weather. There is shed wax on the removable hive floor; there are bees coming and going. It appears that they've been building comb and orienting themselves to their new area. I didn't look for pollen, but I wouldn't expect to see it this soon anyway.

I was very suprised to see a large number of Varroa on the hive floor. I counted 32, which is approximately 9 per day. A conventional bee keeper might urgently treat for Varroa in this situation. I'm inclined to wait and see what happens.

There may be exceptional reasons for the high level of mite drop in this new colony. They were contained for in the skep with a sheet under them before I collected so the varroa may have been shed over a longer time. I whacked the skep to dislodge them so that they fell in a heap on the hive floor. The fall of around 50cm may have dislodged more mites than would otherwise fall. Perhaps this colony is tolerating a higher number of mites. The parent colony seems to be thriving.

Introducing a new swarm to the apiary does raise concerns for me. This colony has not been feral for as long as the colonies from hives C, D and E. They may have genes which help tolerate Varroa and their attendant diseases but it is less likely. This colony may also introduce new strains of viruses which are present in the existing hives. There are known several strains of DWV. I consider this risk low because these strains tend to be geographically separate. It would be unlucky to introduce a new one. There is a risk of exposing the new colony to diseases already present in the apiary. I have seen evidence which suggests ABPV in Hive D.

I'll have to see what happens.

First Varroa drop in my new apairy

Submitted by will on Fri, 27/05/2016 - 17:20

I'd expected that the new bees would bring Varroa. Today I found a dead mite from the colony which I hived earlier this week. It was on the floor of their hive.

The feral colony from which both casts came has apparently been there for 3 years. Today I could see their entrance which had lots of activity. It would appear that they are very strong despite this infestation.