I have found the number of Varroa and the degree of Pyrethroid Resistance in my colonies this year to be very variable. Those I treated with Thymol immediately the honey came off are now dropping only very few mites ( 5 to 30 per day ). I discovered some Apistan strips in a re-sealed pack which were a year past their expiry date and put them into a colony that had had a Thymol treatment for a week and was dropping 130 mites per day. In the next 24 hours they dropped 380 mites. The mite count then quickly went back to 130 mites per day. After 3 weeks of the Apistan treatment the mite count went down to 4 or 5 per day.
When I got some of my colonies back from the Heather I immediately put one of them onto an Open Mesh Floor and started to monitor the Natural Mite Mortality. I recorded 8 to 10 mites per day. When I got their Heather honey off I gave them a Thymol Treatment and recorded 30 mites per day. Then I transfered the 'Out of Date' Apistan Strips that had now been used for 3 weeks in another colony to this colony. To my utter amazement they dropped 790 mites in 24 hours. After 2 weeks of the Apistan Treatment the mite count went down into single figures.
While Re-Queening one of our members colonies I was surprised to find a lot of bees with deformed wings. The beekeeper assured me that he had applied Apiguard exactly as per the instructions as soon as he had taken their honey off. The colony had given a good account of itself during the season and had now gone down hill fast, it covered just 3 or 4 frames with very small patches of brood. There was starved and dead brood present, and the bees were hardly flying at all. We immediately applied a Thymol Treatment and I told the beekeeper that it would be touch and go whether the colony would survive till Christmas. The colony started dropping Varroa mites at over a 100 per day, and after a few days started working normally. He then applied Apistan, the mite count increased to nearly 300 per day! Two years ago at the end of September I saw a colony in almost exactly the same condition which when treated with Thymol dropped 500 mites per day, that colony went on and survived winter. It takes at least 13 days after any treatment is applied before there can be an improvement in the emerging bees. The bees emerging in the following 13 days will have been poorly nursed as grubs by parasitised bees. It will then take yet another 13 days before there is any significant increase in the proportion of un-paracitised bees to produce the bees that will take the colony through winter. The tenacity with which a colony will strive to survive against overwhelming odds is awesome to watch. So much now depends on the what weather we get in the next 4 to 6 weeks as to whether this colony will survive or not.
I don't advocate the wholesale use of Apistan, but if it works why not?
"The price of peace is eternal vigilance" J. F. Kennedy.