The window for doing mite treatments is closing rapidly. You may have missed it as far as winter survival is concerned. However, treat anyways. If you kill the mites in your infected hive you may prevent a varroa/virus bomb that will affect both your neighbor’s hives and any feral colonies in your area.
Check the weight of your hives. The top brood chamber should weigh 80 to 90 pounds. Most of us do not have a scale and must make the measurement by guess and by gosh. Another way is to inspect the frames in the top brood box. At least eight should be capped honey or a substitute. The two center frames should be partially filled. After you lift a few brood chambers so provisioned you will then be able to better gauge a fully provisioned hive. Be careful, don't hurt your back. Simply tipping a fully filled is another way to gauge its weight.
If feeding is required use 2/1 sugar syrup or high fructose corn syrup. Feeding should be accomplished as fast as possible. Provide large volumes (gallons) of syrup via top feeders. Don’t dribble it with quart entrance feeders. The cooler weather also results in the bees being active for shorter times each day. It takes time to move and dry the syrup to 82% sugar concentration. High fructose syrup does not need drying and can be directly stored. The bees will also NOT eat cold syrup. The syrup in entrance feeders cools much more rapidly than internal top feeders. Try to finish your feeding in September.
Please note that the bees see feeding as a nectar flow. Their natural response is to start raising brood. This will permit the varroa to also raise more young. Feeding is a double edged sword, so make sure to re-treat for mites after feeding. Several oxalic acid vapor treatments in late October will kill off the emerging phoretic mites. The goal is to have your hives as mite free as possible going into winter.