(03-18-2010 08:12 PM)Bob Danka Wrote:  Second, we do not think that the mechanism is “pulling too much brood” per se, but rather is principally brood dying from EFB. Third, in the population of very highly selected VSH we maintain here at the lab, some colonies (maybe 10%?) will have brood problems and develop EFB (which, by the way, immediately clears with an oxytetracycline treatment).

Thanks for the input, Bob.

Why is EFB a problem?
Are these colonies more susceptible to EFB then
the population mean, and if so, why do you think this is happening?

Adam Finkelstein

(04-04-2010 07:37 AM)adamf Wrote:  

(03-18-2010 08:12 PM)Bob Danka Wrote:  Second, we do not think that the mechanism is “pulling too much brood” per se, but rather is principally brood dying from EFB. Third, in the population of very highly selected VSH we maintain here at the lab, some colonies (maybe 10%?) will have brood problems and develop EFB (which, by the way, immediately clears with an oxytetracycline treatment).

Thanks for the input, Bob.

Why is EFB a problem?
Are these colonies more susceptible to EFB then
the population mean, and if so, why do you think this is happening?

Adam Finkelstein

Adam,
There are anecdotes about EFB popping up in a variety of hygienic bees but am not aware of any good, direct research on this issue. Let me emphasize that we see this only in some colonies of bees highly selected hygienic bees, not in field colonies. No clear answers, only speculation, as to why it happens.

Bob

(04-04-2010 08:48 PM)Bob Danka Wrote:  Adam,
There are anecdotes about EFB popping up in a variety of hygienic bees but am not aware of any good, direct research on this issue. Let me emphasize that we see this only in some colonies of bees highly selected hygienic bees, not in field colonies. No clear answers, only speculation, as to why it happens.

Bob

One of the reasons of the brood problems may be also sac brood virus (SBV) which I have found last two or three years - most of highly selected hygienic bees apparently removed dead pupea quickly. I realized it in some hives where bees haven't removed dead pupae in time (no the best hygienic), so I found some these pupae dead inside cells - brown coloured (typical sac brood). Requeening these colonies made the brood quality better in a few weeks. By the way, the cause was genetic sensitivity of one line of bees - most of these colonies had the same ancestor from one to three generations ago.
One question - do you somebody know what is the population of mites in VSH colonies? A few hundreds, or thousands? By knowing this it is possible to estimate what a percentage of mite infested brood is removed by VSH bees. Maybe it is low...

Kvetoslav Cermak

Hello Kvetoslav,
Nice to hear about your breeding program. I wish you well in your effort.

You asked about varroa populations in VSH colonies. We (especially John Harbo and Jeff Harris) have measured populations in some colonies during tests. In the best colonies the populations are very low -- typically no more than a few hundred, and often much lower. So in the ideal situation I think that hygienic activity directed at mites does not lead to removal of too much brood. But remember that the broodnest is very dynamic, and brood is being removed because of other problems such as waxmoth larvae, chalkbrood, AFB, perhaps small hive beetles...

Best wishes,
Bob

(04-20-2010 06:08 AM)Bob Danka Wrote:  Hello Kvetoslav,
Nice to hear about your breeding program. I wish you well in your effort.

You asked about varroa populations in VSH colonies. We (especially John Harbo and Jeff Harris) have measured populations in some colonies during tests. In the best colonies the populations are very low -- typically no more than a few hundred, and often much lower. So in the ideal situation I think that hygienic activity directed at mites does not lead to removal of too much brood. But remember that the broodnest is very dynamic, and brood is being removed because of other problems such as waxmoth larvae, chalkbrood, AFB, perhaps small hive beetles...

Best wishes,
Bob

Hello Bob,

thank you for your wish, and the same from Tom Glenn. I have performed only part of the way towards VSH bees. Therefore it is good to discuss some problems here in the forum...

Thank you for good information on the population of mites in VSH colonies. This means that removing some pupae with mites doesn't lead to weeker colonies and therefore it is possible to keep VSH bees purebred - see post #1. Rather reversely - hives with small numbers of mites are not endangered.
I would like to ask another question - is the efectivity of VSH bees sufficient in various climatic conditions? It is known that in colder (temperate) climate mites reproduce more effectively, i.e. population of mites grows quickly comparing to warmer climate...

Kvetoslav

In addition to my previous post and the question there - some data:
No-VSH bee colony (we can say varroa sensitive, VS) may appear to be VSH in conditions unfavorable for reproduction of mites which may happen in warmer climates. It is known that successful mother mite produces about 1.5 viable daughters in a worker cell and that about 70% of mites trying to reproduce are successful in temperate climates. But these two parameters decrease in tropics. It is possible to calculate that the reproduction success only 0.64 viable daughters (on average) is sufficient for balanced population of mites during one year period. The same is true for percentage of reproduction success deceased to 30%. Also combinations of decreasing of both parameters are possible.
In other words - slower reproduction of mites may cause either VSH ability of bees or weather (climate).
What I want to say is that VSH ability of bees is better tested (thoroughly) in colder climatic conditions.

Kvetoslav

(04-27-2010 03:57 PM)Kv.Cermak Wrote:  What I want to say is that VSH ability of bees is better tested (thoroughly) in colder climatic conditions.
Kvetoslav

Hi Kvetoslav,
Great to hear your input! That's an interesting and viable idea.

Adam Finkelstein

(04-27-2010 03:57 PM)Kv.Cermak Wrote:  In addition to my previous post and the question there - some data:
No-VSH bee colony (we can say varroa sensitive, VS) may appear to be VSH in conditions unfavorable for reproduction of mites which may happen in warmer climates. It is known that successful mother mite produces about 1.5 viable daughters in a worker cell and that about 70% of mites trying to reproduce are successful in temperate climates. But these two parameters decrease in tropics. It is possible to calculate that the reproduction success only 0.64 viable daughters (on average) is sufficient for balanced population of mites during one year period. The same is true for percentage of reproduction success deceased to 30%. Also combinations of decreasing of both parameters are possible.
In other words - slower reproduction of mites may cause either VSH ability of bees or weather (climate).
What I want to say is that VSH ability of bees is better tested (thoroughly) in colder climatic conditions.

Kvetoslav

Kvetoslav,
As far as I am aware, bees with VSH have been tested only in temperate climates – not in the tropics and not in the far north. I hope that this forum yields reports about the response to varroa by resistant bees under a range of environments. That could be very instructive.

Environmental factors certainly can influence varroa population growth greatly. However, if everything else was equal, I think that most people would rather manage varroa in a cooler climate with a relatively restricted brood rearing season than in a warmer one where there is a longer brood rearing season.

Bob

Hello Kvetoslav,
Here are some data about the numbers of mites in VSH colonies. Recently we evaluated the varroa populations on adult bees and in brood of two colonies that are headed by open-mated VSH queens. These queens were made in the summer of 2008, and put into colonies that have not been treated since spring of 2008. The colonies were used very intensively for commercial pollination of almonds, apples, lowbush blueberries and cranberries during 2009.

We sampled the colonies a few weeks ago at a time when the major nectar flow period is just about finished here. The measurements showed that each colony has about 400 mites in the brood about 200 mites on the adult bees. These colonies with outcrossed VSH queens functioned well for the beekeeping operation, so this total of 600 mites seems to be a reasonable population to carry.

Interestingly, hygienic activity against mites in brood appears to be greater in one colony than in the other. The ratio of mites in younger sealed brood (larvae, prepupae and white-eyed pupae) versus older sealed brood (purple-eyed pupae) was 10:1 in one colony and 3:1 in the other. Perhaps it will be difficult to answer your question of what percentage of mite-infested brood is removed in this case. We know from much experience that if we introduce an infested brood comb into a pure VSH colony, the bees typically will remove about half of the infested pupae in one week.

Bob

Hello Bob,

thank you for good information giving real data - now I can myself imagine a VSH colony
Also a good piece of information is that free mated VSH queens give fully productive colonies and therefore probably VSH colonies. I suppose that queens were mated in a place where are no drones form VSH colonies (or do not prevail). Similarly, about ten years ago, I compared colonies headed with II queens selected for good hygienic behavior (classical hyg. test) with colonies headed with their free mated daughters - these daughter colonies showed also very good hygienic behavior.

Quote:Perhaps it will be difficult to answer your question of what percentage of mite-infested brood is removed in this case.

It is not necessary to know the value. We can say that fully VSH colony need not remove all brood parasitized with mites.

Kvetoslav