Winter Preparation Is a Fall Activity

The decisions you make in August and September determine how your colonies come through the winter. By the time temperatures drop to where clusters are forming, it is too late to change the outcome for that season. Winter prep is a fall job, and the key variables are mite load going into winter, the health and protein status of the bees being raised as winter bees, and physical colony conditions at the time of cluster formation.

Mite Treatment Timing for Winter Bee Protection

The most critical varroa treatment of the year is the one that protects the winter bee generation. Winter bees are raised in late August through October in most of the US. These bees need to be as free as possible of varroa-associated virus damage (particularly deformed wing virus) to live the 4 to 6 months required to get the colony through winter and into spring buildup.

Treatment timing depends on your latitude and local climate. In most northern US states, the target is to have a treatment with maximum efficacy completed and mite loads below 1 per 100 bees by August 15 to September 1. This means treatments using Apivar (amitraz strips, 6 to 8 week exposure) should be applied by late July at the latest for this timing to work. Oxalic acid vapor treatments require broodless or near-broodless conditions for full efficacy and are most effective in late fall or early spring.

Do not skip a post-treatment mite wash. Many operations apply treatment and assume success without verifying. Check a sample of colonies 4 to 6 weeks after treatment completion and confirm mites are below threshold before assuming winter bees are protected.

Protein Supplementation

Winter bees need to accumulate significant protein reserves (fat bodies) to survive through the winter broodless period and provide nutrition to the spring brood cycle. If natural pollen is scarce in late summer, protein supplementation with a commercial pollen substitute (MegaBee, Global Patties, AP23) directly supports winter bee quality.

Supplement when natural pollen is demonstrably limited: check a sample of hives in your yards for pollen frames in the brood nest. If colonies consistently have fewer than 2 to 3 full frames of stored pollen by August, supplement. Feeding does not replace forage, but it mitigates the impact of a poor late-season pollen environment.

Feed pollen substitute as patties rather than dry powder for best acceptance when colonies are strong enough to work the supplement. Remove any remaining supplement before the colony clusters for winter, as it can grow mold in an inactive cluster environment.

Cluster Strength Assessment

Before overwintering, assess every colony for cluster size. A colony with 6 or more frames of bees going into winter in a standard 10-frame setup has a good probability of surviving in most climates. Colonies with 4 frames or fewer are survival risks unless combined with another weak colony or given significant resource support.

In late October in the northern US, open each hive on a mild afternoon and count covered frames of bees. Log the assessment in your records alongside the colony ID. Use this data to decide which colonies to combine, which to provide feed, and which to document as at-risk going into winter. Operations that do this assessment systematically have dramatically lower unexplained spring losses than those who close up for winter without knowing what they are starting with.

Physical Winter Prep

Reduce entrances to limit robbing and cold air drafts. Ensure hives are level side-to-side and tilted very slightly forward for drainage. In areas with significant snow accumulation, make sure entrance reducers will not become blocked. Moisture management matters more than raw temperature in most climates; provide upper ventilation (a notched inner cover or upper entrance) to allow moisture from the cluster to escape upward rather than condensing and dripping onto the cluster.