>> Early in the season, all the varroa are in drone comb. Later, when the populations get higher, they get less choosy.
> Pete, I question this statement. I also assumed the same. But when I actually went out and used a cappings fork to confirm, my observations did not support that hypothesis.
Hmm. Well I haven't studied it but other people have been looking into this for more than 30 years.
> In colonies of A mellifera carnica infested with Varroa jacobsoni, the invasion of worker brood cells and drone brood cells by reproductive female mites was studied. In 68 choices between brood combs of both cell types, the infestation of mites per cell was, on average, 8.3 times higher in drone brood. This drone cell preference was not affected by the infestation level. It was more marked if drone brood was rare and it decreased towards the end of the drone rearing season.
Here, he seems to suggest the spillover is not due to higher populations of mites but less available drone brood. One problem we had with drone trapping experiments is that bees didn't raise so much drone comb in August, hence you couldn't trap mites that way.
> The mean 8.33-fold preference of drone cells to worker cells by Varroa mites is closely related to the value of 8.6 given by Schulz (1984), who compared 13 pairs of brood combs. A similar value (7.2) was reported by Sulimanovic et al (1982). Within a realistic range of drone cell proportions of 5-15%, the drone cell preference value of 12.1 found in the present study is considerably higher. Though experimental conditions were as uniform as possible, the range of deviations was still very high. This conforms to earlier findings, which showed that the cell infestation behavior of Varroa is variable due to unknown factors (Fuchs, 1985, 1989). A significant decrease in drone cell preference was found with date during the drone rearing season.
This paragraph points out the variability of infestation rates, but confirms that varroa is less choosy later in the season, for whatever reason. Fuchs suggests it's because there is less drone brood and the drones are less well fed.
source
Fuchs, S. "Preference for drone brood cells by Varroa jacobsoni Oud. in colonies of Apis mellifera carnica." Apidologie 21.3 (1990): 193-199.
***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html
|
