Dear B-liners: We are back to debate if tracheal mites can kill bee colonies or not, effectiveness of breeding bees to tolerate mite infestation, resistance as a result of natural selection (survivors of heavy infestation) vs. laboratory selection, breeding and then implementing in our bee population, and relationship between winter mortality and tracheal mite infestations. First of all, I agree with Carry Clark's observations. I have been doing similar work in Ontario for the last 7 years and I found similar results. Bees colonies infested with mites above 40-50% (based on dissection of a sample of 50 bees/ hive) most likely will not make it through the winter. This conclusion was reported by Dr. Otis and Scott-Dupree at the University of Guelph and later supported by my research. There are several factors can effect the survivorship of bee colonies infested with mites. These factors are: 1. Mite prevalence in bee colonies. 2. Bee cluster size in late fall and early spring 3. Length of winter and the average temperature during the winter month. 4. Start of the spring season and the average temperature during spring. 5. Nosema infestation levels and susceptibility of bees to nosema. 6. Bee managements (Feed, providing protection dusring wintering). 7. Location of operation; Canada, northern states, and southern states. Secondaly, I would like to discuss few issues regarding variation of reported winter mortality. For those who reports that bees survived witer without treatment. I like to ask a question. What were the mite infestation leveles in those bee colonies before winter? In most cases , There is no answer. There is no monitoring by sampling bees and dissection to find out what was the mite level in bee colonies before winter. Therfore, the cause of colony mortality may or may not be due to tracheal mites. The assumption of bees with heavy mite infestations or untreated survived winter is wrong. It is unfortunate that most of the winter mortality reports have never mentioned the infestation levels in these hives before winter. Regarding late winter mortality, the tracheal mite infestations can be responsible for late winter mortality and can be complicated by nosema infestations assuming that there is enough feed. Sofar, research have shown in some places and certain operations during certain years there is a positive correlation between nosema infestations and tracheal mite infestations. However, in some years bee colonies with only heavy nosema infestations die in early spring. Other bee colonies with low nosema inestations and high levels of tracheal mites die, too. Befoer we make any conclusions we need qualified data to support these conclustions. Research in tracheal mites is laborious and needs carful experimental designs with appropriate controls and good experience with the biology of bees and tracheal mites (epidemiology). Just to give you an example, I have a beekeeper who complained to me about slow build up of his new requeened colonies in early summer. The beekeeper suggested that the slow build up of his colonies may be due to heavy tracheal mite infestations in these colonies. Though some call the scientists (.......) I did not take this beekeeper's word. I examined the colony and found that the new larvae starved to death though there was a lots of pollen and honey in these colonies. There was no royal jelly in the cells. I took bee samples and examined them for mites. There was no or very low mite infestations. We did examine for nosema and found heavy loads of spores. He could not believe this conclusion because he fed thsese colonies medicated syrup for nosema the previous fall. This example can give an idea about the value of sampling and examination of bee colonies to understand the problem. Rememebr in Canada, tracheal mites have not yet widely spread across the provinces and even within each province. For mite resistance, in early report to this group, I metioned the results of the field test for 17-18 month. We compared mite resistant bees to non-selected bees. In the test, we showed that 90% of the mite resistant colonies had less than 10% tracheal mite infestation (out of these colonies, 40% of the colonies had 0%). For the 8 control colonies, 6 colonies died the first winter due to high mite levels (>50%). This experiment was clear and clean demonstaration to Ontario beekeepers about mite resistant bees. By the way, this experiement was done in one of the Ontario Beekeepers' yards. He did all the managements and no formic acid use. In another note, Konna queens had send two time several frames of hatching brood from Hawaii to Buffalo, NY and I did screen their bees for mite resistance. The test was done in Buffalo, NY. I hope this will shed some lights on the efforts that are done to keep the mites under control in Ontario. Keep your eyes open, sample your bee hives, and treat when it is needed. Good Luck, Mehat Nasr, Ph.D. Ontario Beekeepers' Association c/o Dept. Environmental Biology Univesity of Guelph, Guelph, Ontario Canada