The top 5 reasons colonies die over winter — and what to do about each one this month

Every spring this forum fills with dead-out posts, and most were decided in September. So here's my list from 22 years and a lot of scraped bottom boards, in order: 1. Varroa and the viruses they carry — kills more colonies than everything else combined. The fix happens NOW: treat before winter bees are reared, then verify with a wash. 2. Starvation — including isolation starvation, where the cluster starves inches from honey in a cold snap. Heft in fall, feed to target weight, put candy above the cluster as insurance. 3. Queen failure — old or failing queens quit mid-winter. If her pattern is spotty now, requeen or combine now. 4. Moisture — cold condensation dripping on the cluster. Insulation above the cluster, slight upper vent or quilt box. 5. Small clusters — a softball of bees can't heat itself. Combine them (see the excellent uniting thread this week). Notice varroa is #1 by a mile. Argue with me in the replies.