As part of my evaluation of my breeder queens I was also tracking the mite fall of two mixed breed hives. For the past week the two mixed breed hives have been having a daily mite fall of zero mites.
Previous readers know that my mite control plan is to treat my hives 3 times. One half dose of formic in mid-June, then a full dose of formic the last week of July and then a final fall cleanup treatment with oxalic acid vapor. On October 28th I performed the last oxalic treatment; a single treatment of 2 grams of oxalic. These hives were broodless at this time. Note: a single oxalic treatment of a hive, when broodless, should kill 95% of the mites in the hive.
In the three days following this treatment one hive has dropped 75 mites to the witness board and the second 29 mites. This shows that although the daily mite drop was low (actually zero) that there was still a large quantity of mites in the hive.
This end of season mite treatment will greatly improve the chances of these hives surviving winter.