Deformed Wing Virus in Bees
Deformed Wing Virus (DWV) is a viral infection that damages developing bee pupae, causing adult bees to emerge with crumpled or shortened wings. It’s one of the most common viral diseases in honeybees worldwide, and while it sounds alarming, most colonies survive it—though productivity suffers. Understanding how it spreads and what you can actually do about it will help you keep your hives healthy.
Visible Symptoms
The clearest sign of DWV is exactly what the name describes: bees with malformed wings. You’ll see adults that can’t fly properly, with wings that look shriveled, discolored (often darker), or twisted at odd angles. These bees typically appear near the hive entrance or on the ground in front of it, since they can’t forage and become a liability to the colony. Some infected bees are removed by healthy hive mates (a behavior called hygienic removal), so you might not see many symptomatic bees even if the virus is present.
Other signs are less obvious. You might notice a general decline in colony strength during what should be a build-up period, or see spotty brood patterns where some pupae don’t develop normally. The colony may seem slower to grow in spring. Importantly, DWV doesn’t always produce visible wing deformities—some infected bees show no obvious symptoms but still carry and spread the virus. This asymptomatic infection is actually more common than the dramatic cases.
The severity depends partly on which strain of DWV you’re dealing with (there are several variants) and the overall health of your colony. A strong colony with good nutrition can suppress symptoms and limit spread. A weak colony facing other stressors will show DWV more dramatically.
The Varroa Connection
Here’s the critical link: Varroa destructor mites are the main vector for DWV. The mite feeds on bee hemolymph (bee blood) and, in doing so, transmits the virus directly into the bloodstream of developing pupae. Without Varroa, DWV would be a minor problem in most apiaries. With Varroa, it becomes serious.
When a Varroa mite infests a brood cell, it feeds on the pupa for days while the bee develops. If that mite carries DWV, the virus enters the pupa’s body. The developing bee either dies in the cell or emerges with visible deformities. A single mite can infect multiple pupae in succession, and an infested colony can have hundreds or thousands of mites, creating ideal conditions for rapid DWV spread.
This is why beekeepers in regions with Varroa see DWV regularly, and why it’s almost absent in Varroa-free areas (like parts of Australia). The mite is the disease vector; controlling mites directly controls DWV risk. A colony with low Varroa numbers rarely shows DWV symptoms, even if the virus is present in low levels. A colony with high mite counts will see DWV problems accelerate quickly, especially in late summer and fall when mite populations peak.
Why There’s No Direct Treatment
There is no medication, supplement, or hive treatment that kills DWV inside an infected bee. Antivirals exist in human medicine, but nothing practical or approved for honeybees.
This is frustrating but important to understand: when you see an infected colony, you’re managing the cause (Varroa), not the virus itself. The colony’s own immune system is what clears or controls the infection over time. A healthy colony with adequate nutrition and low mite pressure will often recover from DWV on its own, with fewer deformed bees appearing as the season progresses and the mite population drops.
Some beekeepers sell supplements claiming to boost bee immunity against viruses. While good nutrition (pollen, nectar, or pollen substitute) does support colony health generally, no supplement will eliminate DWV. Don’t waste money on products marketed specifically for viral protection. Focus your effort and money on what actually works: mite control.
Prevention Through Mite Control
The practical solution is straightforward: keep Varroa numbers low, and DWV will not be a serious problem. This means monitoring your colonies for mites (using sticky boards or alcohol washes) and treating when thresholds are exceeded. Treatment thresholds vary by region and season — check with your local beekeeping association or cooperative extension service for the guideline that applies to your area and time of year.
Effective mite treatments include formic acid, oxalic acid, and approved synthetic miticides. Integrated pest management (IPM) approaches—combining cultural methods like drone brood removal with targeted chemical treatments—work better than any single method alone. Timing matters: treat in late summer before populations explode, and again in fall after the brood season ends.
Beyond treatment, maintain strong colonies through good nutrition, avoid overcrowding, and replace old queens regularly. Strong colonies are better at detecting and removing infested brood, which limits mite reproduction. Poor colony nutrition and weak queens make DWV problems worse.
If a colony shows severe DWV symptoms, requeening or combining it with a stronger colony often helps more than any other intervention. Sometimes, culling a chronically weak colony is the most practical choice for the rest of your apiary.