Now is the time to treat for Varroa. Always follow the instructions on the label. There are several products that can be used:
ApiGuard: Thymol Gel, package treats 5 colonies, shelf life is more than a year. Tin of thymol gel. The tin is placed on the top bars of the brood box. Honey must be removed before application. A 1-1/2" shim must be placed on top to raise the roof. Bees need to be able to get to the thymol gel and need the raised space to get the gel. Very safe easy to apply. Temperature critical. If it is to cool this will not work properly. Temperatures should be in the 70's and 80's. Treatment, one tin for two weeks then add another tin. leave both tins on for six weeks. The slide should be in on any screened bottom boards, all holes plugged and the main entrance left wide open.
http://youtu.be/3RGSp3VEeAg
Hopguard II. beta acid made from the hops plant. 24 strips. Treats 12 two deep colonies. easy to use, supers can be left on while treating.
Treatment is two strips per deep. Strips are left in for 14 days. Use rubber gloves when handling. Approved for sale to Wisconsin residents, approval for use in Minnesota is coming very soon.
http://www.betatechopproducts.com/products/varroa-mite-control.php
ApiVar, active ingredient is Amitraz. This is a harder chemical than the previous treatments and may leave residue in the wax. Very effective. 10 strips per package. Treatment: two strips per deep. Leave in for 6 weeks. Use rubber gloves when handling.
http://apivar.net/instructions-for-use/
Mite-Away Quick Strips. Formic Acid gel pads. Package treats 10 hives or 2 hive treatment package.Treatment, 2 gel pads per hive for seven days. Supers can be on the hive. Temperature critical. Do not use if temperatures are over 85 degrees for the first three days of application. A colony should not be disturbed three days before application. Read and follow all instructions. Use rubber gloves when handling.
http://www.nodglobal.com/united-states.html