These contrary findings have always been in the back of my mind when discussing older and reused comb. I had a chance to talk about this survey with the BIP folks and they defended it with some disclaimers but here are the results. See the link for more details.  



> Brood Comb Management and Treatment of Dead Outs: National Management Survey 2011-2012
   

>Comb replacement is often recommended to beekeepers because pathogens, pesticides, and other chemicals can build up in the wax potentially affecting colony health. Beekeepers where asked, on average, how many frames from the brood area they replaced in the last year (0%, 10%, 20%, 25-50%, >50%, Figure 1). Beekeepers who replaced 50% or more of the comb in their colonies lost significantly more colonies (30.7% loss) than those who did not replace any, or 10% of the combs in their brood chambers (22% and 21% respectively). There was some difference based on region. Beekeepers in northern states who replaced 50% or more of the comb in their colonies lost on average 10 more colonies per hundred than those who did not replace any of the combs in their brood chambers. The same comparison was not significant when only looking at southern states.

>https://beeinformed.org/results/brood-comb-management-and-treatment-of-dead-outs-national-management-survey-2011-2012/


Bill Hesbach
Cheshire CT 

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