A new approach for detecting effective reproductive ability of Varroa destructor (Acari: Varroidae).
Roger Strapazzon, Diego Fagundes Kolling, Francisco Estevão Carneiro, Sabrina Alejandra Ramirez, José Carlos Vieira Guerra Jr, Geraldo Moretto
The effective reproductive capacity of Varroa destructor in honey bee colonies is currently calculated on the basis of the number of female deutonymphs found in singly infested worker brood cells at 17-18 days (two to three days before the bee emerges). This calculation presumes that the deutonymphs will reach the adult stage by the time that the adult bee ecloses. Some deutonymphs may not, however, reach the adult phase and there also could be mortality. In order to examine this possibility, we studied mite reproduction in worker brood of Africanized honey bee colonies at 17-18 days and then selected eight colonies in which over 90 % of the infested brood cells contained a single original female mite. The mean proportion of singly infested worker brood cells in these colonies was 96.3 %. Consequently, by subtracting one from the total number of adult female mites found at the time the bee emerged we would be able to estimate the effective reproductive capacity of the original mites, with little error due to the very few cells invaded by more than one original mother mite. Among 377 singly infested worker brood cells analysed at 17-18 days, we found an estimated mean of 1.51 deutonymphs per original female mite. In 250 worker brood cells from the same colonies analysed at bee emergence (two days later) the mean number of new female adult mites was estimated to be 1.07. Thus the effective mite reproductive rate was only 71 % of the original estimate of 1.51. We conclude that the conventional technique of analyzing mite reproduction in 17-18 day old worker brood cells considerably overestimates the actual reproductive rate.