We’ve got some changes to our recommended varroa mite management strategy. Both of these changes have to do with more recent evidence of mite migration from collapsing or infested colonies.
We have previously recommended that August be our final mite check for the year and that once you had the supers off, mites knocked down and hives full of honey, you were done.
We now recommend monthly monitoring until the weather is too cold to disrupt the hive. Into September at least. This is because we’ve heard of the following happening. A mite count was performed in August with the treatment threshold being reached, (7 mites in 300 bees) and the hive was treated with Apiguard. Two weeks post-treatment, another mite count was performed with there only being one mite in the sample. Success right? One month later, in mid-October, another count was done with the results being somewhere in the 40s.
The mites came from other collapsing or heavily infested colonies nearby.
Second, we have told people only to treat colonies where the threshold is exceeded. Again, because of mite migration, we are now recommending that if any one of the colonies in an apiary exceeds the treatment threshold, that all colonies be treated.
Also please remember that good Integrated Pest Management practices call for other means of control before chemical control. The most successful of these being drone brood trapping/sacrifice.