Varroa Infestation Rates by State: What to Expect in Your Region

Mite pressure is not uniform across the United States. A beekeeper in Minnesota experiences very different Varroa dynamics than a beekeeper in Florida, even with similar management intensity. Understanding how regional factors affect infestation rates helps you calibrate your expectations and plan a monitoring schedule that matches your local conditions.

Factors That Drive Regional Differences

The single biggest factor in regional Varroa variation is brood cycle length. In northern states where queens stop laying from November through February or March, there is a natural period when virtually all mites are in the phoretic phase. A properly timed winter treatment during this window can knock down mite populations dramatically. In southern states where queens slow down but rarely stop completely, this natural reset does not occur and year-round mite pressure is the result.

Climate also affects treatment options. High summer temperatures in the Gulf Coast and Desert Southwest limit formic acid use for much of the season. Wet springs in the Pacific Northwest can delay early-season treatments and contribute to higher mite loads through spring.

Africanized honey bee genetics in Texas, Arizona, New Mexico, and California create additional complexity. Colonies with AHB genetics often show different Varroa infestation dynamics and queen behavior that affects management timing.

Northern Tier States (Minnesota, Wisconsin, Michigan, Maine, New York, Vermont, etc.)

The cold winter broodless period is both a management advantage and a risk window. Properly treated colonies entering winter with mite loads below 1% generally winter well. But colonies that were not treated adequately before the broodless period may carry mites through winter on adult bees and emerge in spring with elevated counts, having produced few mites during winter due to lack of brood.

Spring mite counts in the northern tier typically range from 0.5 to 3% depending on fall management. Operations with consistent fall treatment programs average below 1% at first spring inspection. Operations with inconsistent management may be above 2% before buildup even begins, which is a serious problem.

Mid-Atlantic and Midwest (Pennsylvania, Ohio, Indiana, Illinois, Missouri, etc.)

Moderate winters with occasional mild spells mean the broodless window is shorter and less reliable than in the far north. Spring mite counts tend to be higher on average than in Minnesota or Wisconsin because winter broodless periods are shorter. Summer mite pressure peaks in late July and August, and the August through September pre-winter treatment window is critical.

Southeast (Georgia, South Carolina, North Carolina, Alabama, Mississippi, Louisiana, Tennessee)

Year-round or near-year-round brood rearing means there is almost never a complete natural broodless window. The Honey Bee Health Coalition and state extension services in the Southeast recommend treating twice per year as a minimum, with monthly mite monitoring because populations can build quickly in warm months.

Mite pressure in the Southeast is generally higher than in the North on an annual average basis due to continuous brood availability for reproduction. Post-treatment counts confirm efficacy is especially important here because mites can rebound within 6 to 8 weeks.

Pacific Northwest (Oregon, Washington, Northern California)

The mild, wet climate supports long brood seasons. Some operations in coastal areas see year-round brood, while inland areas in higher elevations have more defined seasons. Mite pressure is moderate but consistent monitoring is required due to the extended brood season.

Using Regional Data to Set Expectations

VarroaVault users can track their mite counts longitudinally to see how their operation compares to their historical averages. The Varroa monitoring calendar by region and the varroa management guides for specific states on VarroaVault provide region-specific timing recommendations that account for these differences.

If your mite counts are consistently above average for your region despite a solid management program, consider whether reinfestation from neighboring operations, inadequate treatment duration, or resistance to your current treatment may be factors.