Trevor, Two years ago at the Tennessee State Beekeepers Association Regional Meeting in Memphis we heard about a company that had a machine that would heat your hives to kill varroa( they would do this for a small fee). The state association was going to test this out, but I have never heard anything else about it. I assume it did not work. Bill Hughes Bent Holly Honey Farm Brighton, Tennessee, USA <<I had a visit from a German lady beekeeper last year who had carried out some work at University on using temperature for mite control before becoming a commercial beekeeper. As I recall, they took sealed frames of brood out and heated them to temperatures in the mid 40 degrees celcius. The sealed brood could stand it but the varroa were killed by the temperature. Apparently it was not considered suitable for commercial use as there was only a few degrees difference between the temperature needed to kill the varroa and the temperature at which the sealed brood was killed. If some our beekeeping friends in Germany are on line, they may be able to provide more accurate details. Trevor Weatherhead AUSTRALIA>>