http://www.apimondia.org/apiacta/articles/2007/varroa_reproduction.pdf

Good artice on Costa Rica and Varroa. The last comment is:

Quote:The low mite reproductive ability found in worker brood cells of AHB and HF1 colonies,
seems insufficient to explain the colony losses and reduced production of honey due to
V. destructor reported by beekeepers in Costa Rica. However, infestation rates of
10.0% found in adult bees during a 170-day research study (unpublished data),
indicates that infestation with varroa mites could increase through the year (although
apparently not as high as in temperate climates). Because of mite infestation increase,
most of the beekeepers in Costa Rica have been applying the acaricides Apistan®
(Fluvalinate) and Bayvarol® (Flumethrin) yearly for the treatment of infested colonies.
We hypothesized that, due to the preference of mites to infest drone brood to
reproduce, a high proportion of the mite reproduction should occur in drone cells of AHB
colonies.
Further studies  are needed concerning the reproductive capacity of  V. destructor in
drone brood of AHB colonies, in order to get knowledge with respect to the mite
population dynamic under the tropical conditions of Costa Rica. Unquote

Varroa dynamics are a bit beyond where we think we are. You can get different loads in different climates, so it 
may not be one-size-fits-all. I hear what Dennis says but there are too many variables in this equation.

Bill Truesdell
Bath, Maine

****************************************************
* General Information About BEE-L is available at: *
* http://www.honeybeeworld.com/bee-l/default.htm   *
****************************************************