The Deformed Wing Virus (DWV), also referred to as deformed wing disease, is a viral infection that impacts honeybee hives worldwide. The virus is named after its most noticeable symptom—distorted wings—which develop during the bee’s pupal stage. The affected bees exhibit shrunken, misshapen wings alongside other visible growth abnormalities. This condition represents a major threat, not only to bees but to humans too, given our dependence on bees for ecological balance and food production.
Varroa mites are the key culprits behind DWV, acting as parasitic vectors that transmit a range of diseases deadly to bee colonies. Similar to how mosquitoes spread pathogens in humans, Varroa destructor mites introduce DWV and other illnesses. Because of its significant impact, DWV is among the most researched diseases affecting beehives, with untreated infestations by Varroa mites capable of causing complete colony collapse.
DWV is an RNA virus and is one of twenty-two viruses identified that can be lethal to bees. Some bee species, including Apis mellifera and Bombus terrestris, are particularly susceptible. The first documented cases came from Japan, where the virus was isolated in 1980. Today, the infection is prevalent globally and commonly found in commercially raised bumblebees as well as within bee pollen sacs.
Bees afflicted with wing deformities cannot fly, preventing them from foraging for nectar, pollinating plants, or producing honey—a vital food source for both bees and humans. Over time, this inability to gather resources leads to starvation of the affected bees and diminished pollination in the surrounding environment.
Root Causes of Deformed Wing Virus
Deformed Wing Virus has a well-established link to Varroa mite infestations. Nonetheless, other factors contribute to how a bee colony becomes infected and the disease spreads. The following sections examine the primary contributors to DWV infection and propagation.
1. Varroa Mites
The Varroa mite, scientifically known as Varroa destructor, is an external parasite that feeds on honeybees. It attaches to the bee’s body, weakening the insect by extracting fat stores essential for its survival.
Adult male Varroa mites appear white, while females display a reddish-brown coloration. These mites have a flattened, button-like shape with eight legs, measuring approximately 1 to 1.8 millimeters in length and 1.5 to 2 millimeters in width. Effective treatments targeting Varroa mites can be found here.
2. Insufficient Hive Care
Most modern honeybee colonies are maintained in human-made hives that require ongoing attention. Failure to conduct routine inspections or address early signs of infestation allows diseases like DWV to spread uncontrolled, sometimes resulting in the total loss of the colony. Prompt detection and intervention can preserve the hive and support recovery.
3. Colony Stress
Colonies lacking a robust queen or sufficient population strength are more vulnerable to infections. Such weakened states increase susceptibility to threats from Varroa mites.
Viral diseases in honeybees often remain dormant but can worsen under stress, significantly raising the risk of colony death.
4. Starvation
In winter months, when food reserves drop, honeybees infected by Varroa mites cannot recover due to the mites feeding on their nutrients. Limited nourishment hinders the bees’ ability to maintain their health.
5. Disease Transmission
Occasionally, a hive might receive an intruding bee seeking resources such as food or warmth. If this bee carries Varroa mites, despite defensive actions by resident bees, the virus can spread to the established colony.
The Disease’s Progression
The severity of DWV within honeybee colonies is closely tied to the reproductive cycle of Varroa mites, which is roughly ten days. Female mites invade brood cells and, once sealed, lay eggs on the developing bee larvae. The mites’ growth timeline coincides with that of the bee pupae, hatching as the adult bee emerges from the cell.
Recognizable Signs of Deformed Wing Virus
DWV manifests a variety of harmful effects on affected bees, including:
- Malformations of wings and abdominal regions in adult bees.
- Damage to limbs and appendages.
- Reduction in overall body size.
- Wings that are shortened and nonfunctional.
- Abdomens that appear bloated, shortened, or rounded.
- Discolored or paralyzed wings and legs.
Bees displaying these symptoms typically have a very short lifespan, often surviving only about 48 hours before being expelled by the colony. This behavior helps protect the hive by removing sick individuals early.
Even in the absence of Varroa mites, DWV can persist silently within a colony through covert infections, transmitted orally among worker bees.
Symptoms appear exclusively in adult honeybees and are relatively easy to identify. Varroa mites drain the fat bodies of both larvae and adults, depriving them of vital nutrients which leads to disrupted bodily functions and causes various health problems.
- Disruptions in hormone balance and energy management
- Compromised immune system efficiency
- Reduced ability to neutralize pesticides
- Extreme fatigue and inactivity
Occasionally, mites can be found beneath the abdominal plates of adult bees, specifically on the left side underneath the metasoma area.
Research indicates that mites located under the bee’s abdomen usually feed there, whereas those perched on the top side of the abdomen in the mesosoma region tend to be trying to move onto new hosts rather than feeding.
Varroa mites feed by piercing the bodies of bees, leaving open wounds that make them vulnerable to diseases and viruses. Besides transmitting the deformed wing virus, these mites also spread several other debilitating viruses, with European honey bee species like Apis mellifera being particularly defenseless against these parasites.
Detecting Deformed Wing Virus
Varroa mites are easily identifiable by their oval shape, reddish-brown color, and eight legs, visible to the naked eye. While you can manually inspect hives for these mites, they often hide on bees’ bodies, requiring specific tests to confirm their presence. Several common diagnostic methods are described below.
1. Powdered Sugar Roll Test
This method involves collecting about 300 bees using a half-cup measuring container. Place them in a jar with a mesh lid featuring 1/8-inch holes, then add two tablespoons of powdered sugar. Gently roll the jar for one minute, then invert and shake it for two minutes over a tray to catch the dislodged mites.
To calculate infestation rates, count the mites collected and divide by three to estimate the number per 100 bees. A key advantage of the powdered sugar roll is its non-lethal nature for the bee sample.
2. Alcohol Wash Test
For this test, gather 300 bees using a half-cup measure and submerge them in a jar containing at least 70% alcohol. After sealing the jar, shake vigorously for two minutes. Pour the mixture through a 1/8-inch mesh screen over a collection surface, then count the mites trapped. Dividing the count by three provides the number of mites per 100 bees. Although very effective, this method unfortunately kills the bees used in the sample, which is a significant drawback.
3. Sticky Board Technique
Considered the gentlest method, this technique uses a thick layer of petroleum jelly spread on a board placed beneath the hive’s screened bottom. After three days, the board is retrieved and the number of mites stuck to it is counted. Dividing this figure by three estimates the average daily mite drop per 100 bees. While results take longer, this approach causes no harm to the bees.
4. Soapy Water Method
This approach effectively measures mite infestation by placing 300 bees into a mesh-topped tube filled with soapy water. Shaking the tube dislodges mites, which fall through the mesh. The infestation rate can then be calculated using the formula:
Varroa destructor infestation rate = (number of mites / 100 bees counted)
Approaches to Treating Deformed Wing Virus
Controlling Varroa mite populations is the most efficient way to manage and treat deformed wing virus, which causes colony collapse and bee mortality. Early detection and treatment of mite infestations greatly increase bees’ chances of survival, making preventative action essential.
Effective management of DWV often requires chemical treatments, but a sustainable solution involves breeding honey bees resistant to Varroa destructor mites, offering a long-term approach to this pervasive issue.
Chemical Control Methods for Deformed Wing Virus
On a commercial scale, acaricides are commonly used to combat Varroa mite infestations. Their careful application not only helps reduce mite populations but also minimizes the development of resistance to treatments. However, it is critical to use these chemicals sparingly to prevent honey contamination.
Several synthetic chemical options are available specifically for treating DWV.
Common Synthetic Chemicals Employed Against Deformed Wing Virus
The following list includes synthetic chemicals frequently used to treat deformed wing virus:
- Pyrethroid insecticides such as fluvalinate, often applied as medicated strips.
- Organophosphate insecticides like coumaphos or Check-mite, also delivered in strip form.
- Manley’s thymol crystals administered as a feed supplement.
- A mixture of surgical spirit and sugar given as nourishment during treatment.
Natural Remedies for Deformed Wing Virus Treatment
Several natural substances can be safely utilized to treat Varroa destructor mites, including:
- Formic acid, commonly marketed as Mite-Away, which is applied via vapor release or impregnated pads.
- Powdered substances like sugar or talc with particle sizes between 5 to 15 micrometers, sprinkled directly onto the bees.
- Various essential oils such as lemon, mint, or thyme oils, applied by dripping or via pads.
- Sugar esters like Sucrocide, which are effective when sprayed as a solution in the hive.
- Oxalic acid, applied through vaporization, trickling, or with soaked towels placed inside the colony.
- Edible-grade mineral oils vaporized periodically or applied on absorbent materials like paper or cords inside the hive.
- Natural hop-derived products, such as Hopguard, typically delivered using strip treatments.
Methods of Administering Treatment
Treatments are commonly applied by spraying chemicals directly onto the bee colony, but alternative approaches such as vaporizing or dripping the medication can also be effective. However, spraying acaricides often exposes the bees to these chemicals, which can further weaken a colony already stressed by mite infestation. To avoid this additional harm, administering treatments with gentler techniques is preferable. Below are some practical ways to deliver medication safely:
- Use chemically infused strips coated lightly with sugar syrup or a few drops of it to encourage bees to engage with the treatment.
- Employ the dripping method carefully, ensuring that liquid does not pool in the hive where it could become problematic.
- Aerosol treatments work well but require thorough coverage so every bee receives the medicine during application.
- Place a towel soaked in medication inside the hive; bees will chew on and rub against it, facilitating treatment.
- Opt for edible treatments when possible, as they generally cause fewer adverse effects.
All these techniques can effectively deliver medication to combat deformed wing virus. Selecting the right method depends on your hive’s specific needs, so prioritize your bees’ health when deciding.
Drawbacks of Using Aggressive Chemical Treatments
Overuse of potent chemicals risks contaminating honey, which can harm consumers who eat it. Excessive treatment also endangers the colony’s overall well-being, potentially exacerbating issues rather than resolving them. To prevent these complications, apply only the minimum effective dose. Avoid both over-medicating, which can be toxic, and under-medicating, which allows infestations to persist. Assess the severity of mite invasion carefully before choosing an appropriate treatment plan.
Bees are delicate creatures, vulnerable to both disease and death, so close monitoring is crucial to catch early signs of mite presence. When infestations are mild, gentle treatments usually suffice. But in severe cases, stronger chemical interventions may be necessary, and with their use, the impact on both bee health and honey quality must be carefully evaluated.
The Significance of Bees
Beyond honey production, bees play a vital role in pollinating a vast array of food crops—estimated to be about a third of all crops we consume. Many farmers keep hives near their fields to boost harvests through effective pollination by these industrious insects. Crops such as avocados, soybeans, broccoli, celery, sunflower oil, cucumbers, cherries, cranberries, citrus fruits, peaches, kiwis, and melons all rely on bee pollination. This connection extends directly into our everyday diet, permitting us to enjoy staple foods like almonds and blueberries.
In the United States, roughly 80% of crops depend on honey bees for pollination. Moreover, bees are brought in to support livestock feed production by pollinating clover and alfalfa, thereby influencing the meat and dairy industries. Numerous processed foods incorporate ingredients from bee-pollinated plants, while crops like cotton and flax are heavily reliant on bees too.
Additionally, bees produce beeswax, a substance utilized in cleaning products and a variety of beauty items, exemplifying their contribution beyond nutrition.
Overall, bees are indispensable to humanity in many respects. However, environmental challenges such as climate change and widespread pesticide use have sharply increased the threats to bee populations. Among these threats is the deformed wing disease, which jeopardizes both bee survival and, ultimately, human food security.
Summary
Beekeeping demands dedication, and ailments like the deformed wing virus are unfortunately common. Before resorting to chemical treatments, evaluate the potential consequences carefully. With diligence, patience, and experience, beekeepers can help their colonies endure serious threats. Staying alert and making informed choices are key to supporting healthy hives.