Some people believe that grease patties provide a way to help keep Varroa mite populations low during the winter. This may be true, assuming mite populations are low to start with. A hive that is already heavily infected with Varroa will not benefit from grease patties. Like a screened bottom board, a grease patty most likely has limited value.
According to conventional wisdom, a grease patty with essential oils added—usually wintergreen or tea tree—helps to control mites in two ways. First, the grease tends to get all over the bees, and a slippery surface is difficult for the mites to hang onto. Some research has shown that mite drops may be two to three times greater in the presence of grease patties.
Secondly, the essential oils have a repellent effect on the mites. In addition, some research indicates that if mites come into direct contact with wintergreen or tea tree oil it can kill them outright or interfere with their breeding cycle. Although the EPA does not recognize these oils as being effective, there is much evidence in the beekeeping community that the oils have some effect. Many beekeepers keep grease patties on the hive year-round, but patties with essential oils incorporated into them should not be used when honey supers are on the hive.
Many recipes for grease patties can be found, but the one from the University of West Virginia is quite popular and appears below. The only problem I see with this recipe is the use of honey. If you do not have disease-free honey from your own apiary, do not use honey. I recommend substituting heavy syrup (2 parts sugar to one part water) for the honey unless you are absolutely certain you know the origin of the honey. This point cannot be stressed too much. Honey may contain spores of American foul brood and can easily transmit the disease to your hives. Although, harmless to humans, these spores can wreak havoc on your apiary.
The inclusion of salt provides the bees with essential minerals that they usually get from the environment when they collect water and other materials. Since these products are not collected in the winter, the salt helps to round out the honey bee diet. The sugar and/or honey simply make the patties more attractive to the bees.
The patties can be made in advance and kept in the freezer until you need them. Beekeepers usually place four or five small patties (about 2 ounces each) on the top bars and one just inside the front entrance.
Wintergreen oil can be toxic to humans when absorbed through the skin, so always wear protective gloves when mixing the patties.
Wintergreen grease patties
One batch will treat 8-10 hives. You can easily increase or decrease the recipe size depending on your needs.
4.4 pounds (2 kg) granulated sugar
3 ounces (90 ml) corn oil
1.5 pounds (0.7 kg) vegetable shortening (Crisco)
1 pound (454 g) honey
1/2 pound (227 g) mineral salt (pink color)
2.2 ounces (65 ml) wintergreen oil (or tea tree oil)
Step 1: Pulverize the salt so that it mixes evenly throughout the patty. This also prevents water droplets from forming around salt crystals.
Step 2: Mix all the ingredients thoroughly using protective gloves.
Step 3: Make patties the size of small hamburgers.
Step 4: Store in freezer until ready to use.
By the way, if you can’t find a source of mineral salt—or you don’t want to buy a 50-pound bag—go to your pet store and buy a “bunny wheel.” A bunny wheel is nothing more than a mineral salt lick for rabbits and the bees don’t seem to object to this inclusion of rabbit food in their diet.