A population model for the ectoparasitic mite Varroa jacobsoni in honey bee (Apis mellifera) colonies

The ectoparasitic mite Varroa jacobsoni Oud. presently poses one of the most serious problems faced by keepers of honeybees Apis mellifera L. To help understand why the mite has become such a serious problem a population dynamics model using recently published data has been constructed. The simulation model has been built by linking together various aspects of the mites' biology using computer software (ModelMaker(R)) in such a way that an initial population of mites can change daily over any period. The model predicts a yearly 12-fold increase in mite numbers or an intrinsic rate of daily increase of 0.021 during the presence of bee brood. This corresponds well with field data. Values derived from the model for behaviours such as drone preference (5.5-12 times) and phoretic period (4-11 days) are similar to those actually observed. Therefore, the model can be used to predict the number of mites within any colony and their subsequent development over any period. Since the daily development of both the live population and numbers of dead mites are predicted by the model it can be used as a mite population monitoring tool. The model predicts that the ratio of live to dead mites will change dramatically between periods when bee brood is present or absent. However, since the ratios were shown to be stable within the periods, the mite population can be estimated throughout the year by multiplying the daily mite drop by approximate to 250-500 or 20-40 when brood is absent or present, respectively. This will allow beekeepers to optimise their mite control strategy. The model also reveals the complex pattern in infestation levels that occurred throughout the year which was caused by the interactions between the bee and mite breeding cycles and will allow the role of bee viruses in the collapse of the colony to be studied in much greater detail. (C) 1998 Elsevier Science B.V. All rights reserved.