DeJong found that varroa "prefer" old comb or at least the infestation rate in old comb was much higher than in new, even though the cells of old comb are often much smaller

> Varroa destructor preferentially invades larger honey bee brood cells. Consequently, it was expected that brood in old combs with reduced-size cells would be less infested than the brood in new comb cells. The mean percentage of brood cells infested with V. destructor was significantly higher in the old combs (22.6%), than in the new combs (9.75%), even though the inside width of the cells was significantly smaller in the old (4.58 mm) than in the new combs (4.85 mm). Some factor other than cell size makes old brood comb cells much more attractive to V. destructor than newly constructed brood comb.

> As old dark brood combs normally have the smallest-size cells, and mite infestations in worker brood increase with comb cell size (Piccirillo and De Jong, 2003), we decided to compare mite infestation levels in worker brood reared in old comb with reduced cell size versus that found in new (natural- sized) comb recently built by the bees (without comb foundation).

> We had expected that there would be fewer V. destructor in the smaller brood cells in the old combs than in the relatively larger brood cells in the new combs, as previous experiments had indicated a positive correlation between cell size and infestation rate. However the cells in the old combs were much more infested than those in the new (naturally built) combs (Tab. I), even though the former were significantly smaller. The old comb cells were four to over five times as infested as the new brood comb cells.

Old honey bee brood combs are more infested by the mite Varroa destructor than are new brood combs
Giancarlo A. PICCIRILLO, David De JONG  Apidologie 35 (2004) 359–364

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