What a Mite Threshold Means: HBHC's Table 1 by Colony Phase

A mite count only means something next to a threshold, and the Honey Bee Health Coalition's (HBHC) 9th edition, current as of June 11, 2026, sets that threshold by what stage the colony is in rather than by the date. This page explains what each phase is and what crossing its threshold means; the varroa calculator does the actual comparison against a count you enter.

The four phases

HBHC's Table 1, titled "Table 1: Varroa Mite Treatment Thresholds by Colony Phase (%=Number of mites/100 adult bees)", sets a threshold for each of four phases a colony cycles through:

• Dormant (less active): "Bees are clustered; little or no brood in northern locations and reduced brood rearing in southern locations; all or most varroa mites are on adult worker bees; bee and mite populations are in decline because little or no reproduction is occurring within the colony." Threshold: ≥1%.
• Population Increase: "Seasonal colony buildup; colony brood and adult worker population increasing; varroa population usually low but increasing; pre-honey flow supering of colonies." Threshold: ≥1%.
• Population Peak (Table 1 prints it "Peak Population"): "Bee population (both adult and brood) at peak; mite populations increasing, nearing peak; often honey supers on colonies." Threshold: ≥2%.
• Population Decrease: "Post-honey harvest; bee population decreasing; colonies rearing overwintering bees. Varroa populations growing, peaking, and then declining until eventually only phoretic/dispersal mites on adult bees after colonies have little or no brood." Threshold: ≥2%.

Below its phase's line, HBHC calls the count acceptable, in the table's own column heading: "Immediate control not needed". At or above it, the table's other column reads "Promptly control". The Dormant row carries a footnote about timing a sample: "*Note: Sample just prior to clustering to determine whether bees are healthy going into dormancy."

Why phase, not month

HBHC never assigns a phase to a calendar month, and this site follows that: "In some locations, there is one cycle of these four phases per year, in other locations there can be more than one cycle." A colony in Florida and a colony in Minnesota can be in different phases on the same date, and a beekeeper who isn't sure which phase applies can pick "Not sure" on the varroa calculator to see the verdict for all four at once rather than guess. None of the nine regional calendars assigns an HBHC phase to a month either; where a calendar mentions mite monitoring, it links to the calculator instead of repeating a threshold.

What crossing the threshold means

HBHC spells out both directions. Below the line: "When mite levels are below the threshold, the infestation is considered acceptably low, so immediate control may not be needed at that time." At or above it: "When mite levels are above the threshold, apply mite control immediately, using a registered, effective, seasonally appropriate treatment method according to label directions" — and from there HBHC's own sentence points into its table of control options by phase. Neither this page nor the calculator names a product or dose; that table, in HBHC's own guide, is where treatment options are.

When to sample again

HBHC also sets a rhythm for re-checking, not just a one-time number: "Generally, a beekeeper should perform varroa monitoring assessments monthly beginning with the Population Increase phase, or at least 4 times from Population Peak to Decline." The stakes rise as the season turns: "Having a low mite population at the start of bee Population Decrease phase is critical. If mite populations are high, the colony may not be healthy enough to rear bees to survive the dormant phase." A single count is a snapshot; the pattern across a season is what actually tells you whether a colony is heading into winter in good shape.

What this page leaves out

Only the 9th edition's numbers are used here. HBHC's earlier, higher thresholds from its 8th edition are shown nowhere on this site except the What changed page, which explains the revision; using the older numbers anywhere else would tell a beekeeper not to act when HBHC's current guide says to. An older, separate 3-per-100 level that some other sources still print is a different figure again, not HBHC's; the varroa calculator shows it only on a row labelled as older guidance, next to its own sources.