VTBeeHannah · Vermont, US · Pests & Disease · Sep 28, 2026

What mite count is actually acceptable going into winter — is 3 per 300 in late September good enough, or is 5 too many?

Second year in Vermont, three hives, and I'm confused about which mite number I should be aiming for right now. Ran Formic Pro in mid-August (two strips, 14 days, temps cooperated for once). Did verification alcohol washes yesterday — half cup of bees from the brood nest each — and got 1, 3, and 5 per 300. All summer the rule I learned was "treat at 3%, which is 9 per 300." By that logic all three hives are fine. But my mentor looked at my numbers and said the 5 is too high going into winter and the target is under 1%, so 3 or fewer. Those are very different thresholds and nobody has explained to me WHY the number changes with the season — is it just that people get more cautious in fall, or is something actually different about the biology? And practically: is the hive at 5 in trouble, or is that a "do oxalic once she's broodless" situation rather than a "do something this week" situation? First frost is probably ten days out.

#varroa#alcohol-wash#winter-prep#oxalic-acid#thresholds

▲ 1 votes 💬 2 replies ✅ Solved

2 replies

ImkerinLena · Sep 28, 2026 · ✅ Accepted answer

Something is genuinely different, it isn't caution. The summer 3% figure is an action threshold for a big, growing colony that still has time to raise clean winter bees. By late September those bees are already raised, and the arithmetic turns: the colony shrinks from perhaps 30,000 bees to 10,000 by November while the mites stay in the box, so 5 per 300 today can be 12-15 per 300 on the bees that remain, feeding on their fat bodies all winter. Hence the goal of ≤3 per 300, ideally 0-1. Your 1 and 3 are fine; the 5 gets one oxalic treatment once broodless, per the Api-Bioxal label.

GeorgiaWes · Sep 28, 2026

ImkerinLena said it better than I would. One thing I'd add from 22 years: a colony that washes higher than its sisters after the same treatment is often the one that's been robbing a collapsing hive somewhere in the neighborhood and bringing mites home. So don't assume the formic failed — it may have worked and she reloaded. Reduce her entrance if you haven't, and yes, oxalic when broodless. Your other two get the same round on the same day; treat the yard, not the hive.

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