On Sun, 8 Apr 2007 14:51:25 +0000, Gavin Ramsay <gavinrbox-
[log in to unmask]> wrote:

>Steve asked:
>
>> 1. How many years can you safely use brood comb?  It seems
>> like you could have virus infected comb after one season
>
>.. it would seem that Varroa and its saliva does carry some picorna-like 
viruses and could be a vector, but also the queen lays virus-contaminated 
eggs and that worker to larva transmission takes place.  Simply renewing 
comb is unlikely to break the cycle of infection with this and related 
viruses, and so I doubt that comb renewal could be justified on this issue 
alone.

On Sun, 8 Apr 2007 14:51:25 +0000, Gavin Ramsay 
<[log in to unmask]>
wrote:

>Yet comb renewal has become a popular call - does anyone have concrete
evidence of a benefit from comb renewal, beyond the possibility of 
relief
from Foulbrood, Nosema and perhaps Chalkbrood?

The case for the three diseases you state above have been demonstrated
experimentally. The level of comb replacement used to get the reduction in 
these studies, however, is fairly high (typically all the comb is 
replaced).  I know of only one study tracing the benefits of disease 
reduction by routine replacement of *a portion* of a colony's comb... it 
was from Sweden, it involved annual replacement of some of the combs for 
Nosema reduction.  I recall the partial replacement resulted in 
significant Nosema reduction, but it underscores the dearth of research 
into the benefits of partial comb replacement.  

RE: the benefits of comb replacement will extending to viruses.  I 
disagree that recent findings that point to the agency of the workers, 
queens and drones in the transmission of these viruses, means that comb 
replacement won't have any benefits.  Remember the transmission of AFB, 
EFB, Nosema and chalkbrood ALSO depends on the activity of nestmates... 
these diseases don't just waft out of the comb on their own... nonetheless 
the evidence suggests that comb replacement can reduce all of these 
diseases. I am unaware of any study that has *even* investigated the 
benefits of comb replacement in reducing viral infections... we are far 
from a verdict in this area.

Then, of course, there is Allen's point about residues.  Dr. Pettis at the 
USDA has done a nice job determining the lethal and sublethal effects of 
coumaphos residues on the colony.  The work suggests that colony 
performance would benefit from comb replacement, but again, this has not 
been investigated directly and experimentally.  It would be nice to see 
more work looking at the benefits of comb replacement in the absence 
diseases, so as to focus on *all other factors* associated with comb 
repacement.

To round this discussion out I think it is useful to revisit the work from 
the Univerity of Georgia (Berry and Delalane 2001) looking at the 
development of colonies on new and old comb.  I recall that they observed 
higher survival for brood reared on dark old comb compared to new comb.  
The picture is made even more complicated when you factor in the 
economics.  

I think there is a lot more to know about comb replacement.  I am equally 
concerned when people evoke comb replacement as a panacea as when people 
write it off as inefficient. I agree with Gavin... comb replacement will 
only become adopted more widely when the accounting of the benefits 
accrued by partial comb replacement are better defined. 

Adony

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