Bald brood

[Curly green finger's]

Hi morning, speaking to a few beeks recently the conversation went on to low varroa counts this year but more bald brood.
I thought I would ask here about "bald brood" and hopefully learn more about it.
Thanks
CGF.

 

[jenkinsbrynmair]

Bald brood is one of the indicators of a heavy varroa infestation - how did they ascertain their 'low varroa counts'

 

[masterBK]

In my experience the majority of bald brood relates to the activities of the greater wax moth larvae. These tend to be in lines and the house bees have removed the silk generated by the WM larvae although you can also find the silk tunnels and the black faeces of the WM larva to confirm. Have also come across a few cases of genetic bald brood (which tends to be an indicator of inbreeding). Some of genetic version cases also had sac brood (also linked to inbreeding susceptibility). I have yet to see any bald brood associated with heavy infestation with Varroa . Is that the result of hygienic behavour or part of PMS (parasitic mite syndrome)?

 

[jenkinsbrynmair]

In my experience the majority of bald brood relates to the activities of the greater wax moth larvae.

In my experience it was nothing to do with greater waxmoth.
The National Bee Unit are of the same opinion - heavy varroa mite load

 

[Curly green finger's]

In my experience it was nothing to do with greater waxmoth.
The National Bee Unit are of the same opinion - heavy varroa mite load

This is what sperd me on to ask about bald brood, I've had a little read about the cause being wax moth which wouldnt stand up to lower varroa counts. IF it was caused by heavy varroa.

 

[jenkinsbrynmair]

This is what sperd me on to ask about bald brood, I've had a little read about the cause being wax moth which wouldnt stand up to lower varroa counts. IF it was caused by heavy varroa.

Well a lot depends on how they measured the varroa levels to start with, using a drop board is akin to forecasting the weather with a bit of seaweed.

 

[jenkinsbrynmair]

I have yet to see any bald brood associated with heavy infestation with Varroa . Is that the result of hygienic behavour or part of PMS (parasitic mite syndrome)?

Possibly more to do with hygienic behaviour - nowhere near as severe/down to the final line as PMS SBI's are seeing it quite often in colonies with high but not worryingly high levels of varroa.
I noticed it, combined with DWV at an apiary with powerfully strong colonies towards the end of the season. This apiary does have issues as it's in an area liberally dotted with leaveitalone beekeepers who invariably have autumn deadouts which they leave to be robbed out in the hope of attracting a spring swarm

 

[Erichalfbee]

I have yet to see any bald brood associated with heavy infestation with Varroa . Is that the result of hygienic behavour or part of PMS (parasitic mite syndrome)?

I had a visit from my SBI this summer as part of a foul brood alert. I had one colony that was in trouble with varroa. I had spotted it and was taking action. We looked through it together and there was a lot of bald brood. She told me that was pathognomic of a heavy varroa infestation and that’s what the NBU was advising.

 

[jenkinsbrynmair]

pathognomic of a heavy varroa infestation

Is that the same as being indicative of a heavy varroa load?

 

[Erichalfbee]

I like to use these medical words now and then

 

[Gilberdyke John]

I like to use these medical words now and then

Careful with that - it might cause cranial odema

 

[mbc]

. This apiary does have issues as it's in an area liberally dotted with leaveitalone beekeepers who invariably have autumn deadouts which they leave to be robbed out in the hope of attracting a spring swarm

It's the traditional West Wales way

 

[oxnatbees]

Prof Martin at Salford be University makes the point that patches of bald brood .may be temporary if you have bees that uncap/recap to check on varroa. Ie if you were to check those frames later the cells would be recapped, with some empty cells where infested larvae have been removed. Such bald brood cells would have ragged holes.

This would be a genetic trait.

 

[rampino]

I was inspected by our SBI over a month ago. He was looking for sacbrood or foulbrood of which I had neither.
There was some baldbrood, however, which he said was due to high varroa levels. There was varroa, which I have since treated with Apivar, but no sign of wax moth.

 

[Finman]

In my experience it was nothing to do with greater waxmoth.
The National Bee Unit are of the same opinion - heavy varroa mite load

My experience is too, that bald brood is result of bad varroa load.

Once we had two nucs made from a big hive's brood. After 2 weeks in boath nucs amount of bees had dimishes and there were quite much baldbrood. After a month boath colonies were dead.

 

[RichardK]

I experienced bald brood in two colonies this season. One in a nuc and the other a 10 frame hive, but neither particularly strong. I undertook no treatment but due to line markings in places on the brood tried to find wax moth larvae but couldn't...I just made a mess instead

I did not treat for varroa as I hadn't realised it was even a possibility. As the colonies grew the problem disappeared which I doubt would have happened had it been due to varroa.

This is a link to an interesting article explaining and illustrating how bald brood may be caused by moth or varroa infestations. It also talks about / shows how to interpret bald brood on a frame to work out which (moth or varroa) is the culprit.
Bald Brood – Bee Informed Partnership

And this Feb 2021 PDF download linked from the National Bee Unit is also interesting: https://www.nationalbeeunit.com/downloadDocument.cfm?id=1447

 

[masterBK]

Wax moth derived and genetic bald brood usually continues to grow and develop in the unsealed cell. In my attached photo you can see two workers in their unsealed cells almost at the point of emergence. In one form of genetic bald brood those larvae that lack the right gene don't release or don't release enough capping pheromone ( certain esters of fatty acids in brood pheromone) at the appropriate time so the attendant workers are not stimulated to seal their cells.