How to Monitor Varroa: Alcohol Wash, Sugar Roll, and Sticky Boards

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title: "How to Monitor Varroa: Alcohol Wash, Sugar Roll, and Sticky Boards" category: "Varroa Management" summary: "Monitoring is the only way to know whether your Varroa load is at a safe level or approaching colony-threatening territory. Here's how to do an alcohol wash — the gold standard — and when each method is appropriate." readTime: 8 difficulty: "beginner" season: "year-round" slug: "varroa-monitoring-methods" publishedAt: "2026-03-08" course: "beginner" module: "Varroa Management" lessonOrder: 10

You cannot estimate your mite load by watching the hive entrance. You cannot tell from a strong-looking colony or from how well your bees were doing last month. Colonies with high Varroa infestations look perfectly normal — until they collapse. The only way to know your infestation level is to measure it, and the only way to measure it reliably is with a standardized sampling method.

This article walks through the three main monitoring methods, when to use each, and how to do an alcohol wash correctly.

Why Monitoring Is Non-Negotiable

Varroa populations grow geometrically. A colony at 1% infestation in July can reach 4–5% by September if untreated. At 3%+, Deformed Wing Virus is typically amplifying rapidly through the brood, shortening adult bee lifespan and compromising the colony's ability to rear the long-lived winter bees it needs to survive.

The Honey Bee Health Coalition Varroa Management Guide is clear: regular monitoring is the foundation of effective Varroa management. Treatments applied without monitoring are either premature or too late — rarely correct.

The Three Methods Compared

Alcohol Wash (Gold Standard)

The alcohol wash is the most accurate method available to hobby and professional beekeepers. It kills mites on contact, washing them off the bees into a visible liquid where they can be counted precisely. The HBHC and Penn State Extension both recommend it as the primary method for threshold-based decision making.

Accuracy: High. When done correctly, captures ~96–98% of phoretic mites on sampled bees.

Drawback: It kills approximately 300 bees per sample. This is less than 1% of a healthy colony's adult population, and is not harmful to the colony. It is, however, a psychological barrier for some new beekeepers.

Sugar Roll

The sugar roll uses powdered sugar to dislodge mites from a sample of bees, which are then shaken over a white surface and counted. Bees are returned to the hive alive.

Accuracy: Lower. Sugar rolls typically detect 40–70% of phoretic mites, meaning a 2% infestation might register as 1% or less. This is a meaningful difference when you're making treatment decisions at threshold.

When it's appropriate: If you have a strong objection to the alcohol wash and understand the method captures fewer mites, a sugar roll is better than no monitoring. Adjust your mental threshold downward — if you see 1.5% on a sugar roll, the real number may be closer to 2–3%.

Sticky Boards

A sticky board placed under a screened bottom board counts mites that fall naturally from bees over 24–72 hours. It's passive and requires no bees to be sacrificed or disturbed.

Accuracy: Low for threshold decisions. Mite drop is influenced by colony size, brood stage, temperature, and bee behavior in ways that make translating counts to infestation percentages unreliable. The HBHC does not recommend sticky boards as the primary method for threshold-based decisions.

When it's useful: Sticky boards are good for detecting whether mites are present at all, or for tracking relative trends over time in the same hive. If you see zero mites on a 48-hour sticky board in a populous colony, that's genuinely informative. If you see a large spike after treatment, it confirms treatment is working. But for deciding whether to treat, use an alcohol wash.

How to Do an Alcohol Wash

You need: a wide-mouth quart jar with a mesh lid (or two-jar wash kit), 70% isopropyl alcohol, and a measuring cup.

Step 1: Collect Your Sample

• Find a frame with open brood and nurse bees — this is where mites concentrate.
• Shake or brush approximately 300 bees (roughly a half cup by volume) into your collection jar. Do not sample from honey frames or the outermost frames, where mites are underrepresented.
• You do not need to find the queen, but avoid sampling a frame she's actively on. If you see her, move to the adjacent frame.

Step 2: Add Alcohol and Shake

• Pour enough 70% isopropyl alcohol into the jar to fully submerge the bees.
• Secure the lid and shake vigorously for 60 seconds. This dislodges phoretic mites from the bees' bodies.

Step 3: Strain and Count

• Pour the liquid through the mesh lid (or a second jar with mesh) so the alcohol and mites pass through while bees are retained.
• Pour the strained liquid into a white container — a white bucket lid or a shallow white dish works well.
• Count the mites. They are small (about 1.5mm), reddish-brown, and will be clearly visible against the white background.

Step 4: Calculate Your Infestation Rate

Divide the mite count by the number of bees, then multiply by 100 to get a percentage.

A half cup of bees is approximately 300 bees. So:

Mites counted ÷ 300 × 100 = % infestation

| Mites counted (per 300 bees) | Infestation % | Action | |---|---|---| | 0–3 | 0–1% | Monitor monthly; treat before winter buildup if close to 1% | | 4–6 | 1.3–2% | Approaching threshold; increase monitoring frequency | | 6+ | 2%+ | Treat immediately (HBHC summer threshold) | | 3+ in Aug–Sep | 1%+ | Treat immediately (pre-winter threshold) |

Treatment Thresholds

The HBHC Varroa Management Guide defines two thresholds:

• ≥2% during the active season (spring through midsummer): Treat immediately.
• ≥1% in late summer (August–September in the Northern Hemisphere): Treat immediately.

The lower late-summer threshold exists because the bees being raised in September are winter bees — the long-lived individuals the colony depends on for survival. Varroa exposure during their pupal development permanently reduces their fat body mass and longevity. A colony that raises its winter bees under heavy mite load will likely fail by February even if treated in October.

Monitoring Frequency

• Every 30 days during the active brood-rearing season (typically April through September in most of the U.S.).
• Before any treatment: Know your starting infestation level.
• After treatment: Monitor again 3–4 weeks after completing a treatment to confirm it worked. If your post-treatment count is still ≥2%, you may be dealing with treatment resistance or application error.
• Late fall/early winter: One final monitoring before the colony clusters, to confirm the winter bees are starting clean.

Key Takeaways

• The alcohol wash is the most accurate monitoring method and should be your primary tool for threshold-based decisions. A half-cup sample (~300 bees) is the standard.
• Sugar rolls undercount mites by 30–60% — if you use one, treat the result as a lower bound, not the real number.
• The treatment threshold is ≥2% during the active season and ≥1% in late summer. These numbers come from colony population dynamics, not guesswork.
• Monitor every 30 days during the brood season, always before treatment, and always 3–4 weeks after treatment.
• If your post-treatment count doesn't drop significantly, investigate treatment application, temperature, and resistance before assuming the mites are gone.