Isis Glass wrote:

>14% mites in Autumn is probably high enough to kill the hives over winter.

In order to winter successfully the level should be much lower. Using the
information below, Johnsen's number (14%) translates to 50 mites per 350.
They say winter mortality will be 25% if the rate is 3 or 4 percent.

> Varroa Mite Threshold Study Conducted in Pennsylvania by Dennis Van
Engelsdorp and Jim Steinbauer.

> Utilizing the Sugar Roll method of surveying if you wish to not lose over
10% of your hives during the winter you should treat if less than 4 mites
show up in the sugar roll (about 350 bees). If you don’t want to lose over
20% then treat if between 4 and 12 mites show up. If you do not want to lose
over 25% then treat if 13 or more mites show up.

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