Varroa Mite Treatment Guide

If you keep bees, you keep varroa mites. These parasites arrived in the US in 1987 and have been the leading cause of colony losses ever since. There is no "varroa-free" beekeeping in most of the world—only varroa-managed beekeeping. This guide will teach you to test, treat, and keep your colonies alive.

What Are Varroa Mites?

Varroa destructor is a parasitic mite that feeds on honey bees. Adult female mites (about the size of a pinhead, reddish-brown, oval-shaped) attach to adult bees and feed on their fat bodies. But the real damage happens in brood cells.

Female mites enter brood cells just before capping and reproduce inside. A single mite entering a drone cell can produce 2-3 daughters; in worker cells, 1-2 daughters. When the bee emerges, the mites hitch a ride and spread to other bees—and eventually other cells.

How Varroa Kills Colonies

• Direct parasitism – Feeding weakens bees, shortens their lifespan
• Virus transmission – Varroa spreads Deformed Wing Virus (DWV), Acute Bee Paralysis Virus, and others. This is often what actually kills colonies.
• Weakened immune systems – Parasitized bees are more susceptible to other stresses
• Winter death – Bees raised with high mite loads are too weak to survive winter, leading to colony collapse in late winter/early spring

How to Test Mite Levels

You can't manage what you don't measure. Testing is non-negotiable. Do it at least 3 times per year: spring, mid-summer, and late summer/fall.

Alcohol Wash (Most Accurate)

The gold standard for mite testing:

1. 1. Collect approximately 300 bees (½ cup) from a brood frame into a jar with alcohol (rubbing alcohol or windshield washer fluid)
2. 2. Shake vigorously for 60 seconds—this dislodges mites from bees
3. 3. Pour through a mesh strainer or use a commercial mite wash container
4. 4. Count the mites
5. 5. Calculate: (mites ÷ bees) × 100 = mite percentage

Yes, this kills ~300 bees. It's worth it. A colony has 40,000-60,000 bees; losing 300 to know your mite load is a small price.

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Sugar Roll (Less Accurate but Non-Lethal)

Same process, but use powdered sugar instead of alcohol. Shake, let sit 2 minutes, shake again, then sift onto white paper and count mites. Bees can be returned to the hive.

Downside: less accurate (doesn't dislodge all mites), messy, and the "non-lethal" aspect is often overstated—bees are stressed and some die anyway.

Sticky Board (Passive Monitoring)

A sticky board under a screened bottom board catches mites that fall naturally. Count after 24-72 hours and divide by days. Useful for monitoring trends but not as accurate as wash methods for determining treatment thresholds.

Treatment Thresholds

Not every mite requires treatment. The goal is to keep populations below damaging levels, not eliminate them entirely (which is impossible).

Example: If your alcohol wash yields 9 mites from 300 bees, that's 9 ÷ 300 = 0.03 = 3%. Time to treat.

Treatment Options Compared

*Oxalic acid is most effective when broodless; efficacy drops with capped brood present.

Organic Treatments

Oxalic Acid

A naturally occurring compound found in many plants. Very effective against mites on adult bees, but doesn't penetrate capped brood cells.

• Vaporization – Heat oxalic acid crystals to create a vapor that fills the hive. Most effective, requires special equipment. 1-3 treatments spaced 5-7 days apart.
• Dribble – Dissolved in sugar syrup and dribbled between frames. Easier but less effective and can be hard on bees.
• Best timing – Late fall or winter when colony is broodless. All mites are on adult bees = maximum kill.

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Formic Acid (Formic Pro, MAQS)

Penetrates capped brood cells—one of few treatments that kills mites inside cells. Strong chemical smell; can cause queen loss if applied incorrectly or in high heat.

• Application – Strips laid across top bars for 7-14 days
• Temperature – 50-85°F. Too hot causes bee kill and queen loss.
• Can use with supers – Won't contaminate honey

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Thymol (ApiGuard, Apiguard)

A plant-derived compound with moderate efficacy. Bees distribute it through normal activity.

• Application – Gel in a tray placed on top bars; two applications, 2 weeks apart
• Temperature – 60-105°F for proper evaporation
• Note – Strong odor can taint honey; don't use during flow

HopGuard 3

Hop-based compound on cardboard strips. Gentler on bees but lower efficacy. Good for light infestations or maintenance.

Synthetic Treatments

Apivar (Amitraz)

The most widely used and consistently effective varroa treatment in the US. Plastic strips containing amitraz are placed in the brood nest for 42-56 days.

• Efficacy – 95%+ when used correctly
• Temperature – Works at any temperature
• Resistance concern – Some mite populations have developed resistance; rotate treatments annually
• Cannot use during honey flow – Remove at least 2 weeks before supers go on

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When to Treat

Integrated Pest Management

Treatments alone aren't enough. Combine chemical control with mechanical and cultural methods:

Mechanical Methods

• Drone brood removal – Varroa prefer drone cells (longer development = more reproduction). Remove drone comb periodically to trap and destroy mites.
• Screened bottom boards – Mites that fall off bees can't climb back up. Removes some mites passively.
• Brood breaks – Caging or removing the queen temporarily breaks the brood cycle, denying mites reproduction sites.

Cultural Methods

• Requeen with resistant stock – Some bee lines show varroa-sensitive hygiene (VSH), Russian, or other resistance traits.
• Small cell foundation – Theory is smaller cells reduce mite reproduction. Evidence is mixed.
• Strong colonies – Healthy, well-fed colonies manage mites better than stressed ones.

The "Treatment-Free" Question

Some beekeepers advocate not treating for varroa, arguing that natural selection will produce resistant bees. While there's merit to breeding for resistance, here's the reality for most beekeepers:

• Treatment-free beekeeping leads to very high colony losses (often 50%+ annually)
• Dying colonies "share" their mites with neighbors through robbing and drifting
• It takes many years of losses to potentially develop resistant stock
• Most hobbyists can't afford 50% annual losses

Our recommendation: Treat your bees. Use organic methods if you prefer. But don't let colonies die "naturally" while hoping for resistance. That's a long, expensive, heartbreaking path.

Your Mite Management Plan

Here's a simple annual schedule:

1. March/April: Test. Treat if needed (Apivar or Formic Pro).
2. June: Test. Monitor during nectar flow.
3. August: Test. This is critical—treat before winter bee production if above 2-3%.
4. November/December: Oxalic acid vaporization when broodless (if possible).

Test, treat when thresholds are reached, rotate treatments, and repeat. It's not glamorous, but it keeps bees alive. And that's the point.