8 Common Bee Diseases & How to Prevent Them: A Beekeeper’s Guide

Nothing is more disheartening than opening a hive to find signs of disease that could threaten your entire apiary. The good news? Most bee diseases can be prevented with proper management techniques and early intervention.

In this comprehensive guide, I’ll walk you through the most common diseases affecting honey bees, how to identify them, and most importantly, how to prevent them from taking hold in your colonies. Whether you’re a novice beekeeper or a seasoned apiarist, this information will help you maintain thriving, resilient colonies.

Bacterial Diseases

American Foulbrood (AFB)

American Foulbrood is perhaps the most dreaded disease in beekeeping. Caused by the spore-forming bacterium Paenibacillus larvae, it specifically targets bee larvae, killing them after they’ve been capped.

How to Identify AFB:

• Irregular brood pattern with sunken, perforated cappings
• Dark, melted-looking larvae that turn into a ropey, sticky mass
• Distinctive foul odor similar to rotting fish
• “Pupal tongue” – remains of the larval tongue sticking up
• Coffee-colored scales that adhere tightly to the cell wall

I’ll never forget my first encounter with AFB. Opening a previously thriving hive to find that telltale spotty brood pattern and detecting that sickly smell was a gut-wrenching experience. When I inserted a twig into a cell and pulled out a brown, stringy substance that stretched over an inch before breaking, I knew I was dealing with something serious.

Prevention Strategies:

1. Purchase bees and equipment from reputable sources
2. Regularly inspect brood frames, particularly checking for irregular patterns
3. Never feed honey from unknown sources to your bees
4. Sterilize used equipment before introducing it to your apiary (scorching wood surfaces or using gamma radiation)
5. Replace 20% of your brood comb annually

Treatment Options: Unfortunately, once AFB is confirmed, most regions require the destruction of the affected colony and equipment by burning, followed by burying the ashes. The spores can remain viable for over 70 years, making this disease particularly persistent. Some areas allow treatment with antibiotics like Terramycin, but this only controls symptoms without eliminating spores.

European Foulbrood (EFB)

Unlike its American cousin, European Foulbrood is less deadly but still serious. Caused by Melissococcus plutonius, EFB typically affects unsealed larvae.

How to Identify EFB:

• Twisted, discolored larvae in unsealed cells
• Yellow or brown larvae instead of the healthy pearly white
• Sour odor, less pronounced than AFB
• Larvae die in a twisted position, often curled up or stretched out
• Remains are less ropey and more granular than AFB

Prevention Methods:

1. Maintain strong colonies with plenty of nurse bees
2. Ensure adequate nutrition, especially protein from diverse pollen sources
3. Avoid stressing colonies with excessive inspections or manipulations
4. Maintain good ventilation in hives
5. Replace old brood comb regularly

Treatment Approaches: The good news about EFB is that strong colonies can often recover on their own once stress factors are removed. In severe cases, antibiotics may be prescribed by a veterinarian, but the better approach is usually to:

• Remove and destroy heavily infected combs
• Reduce stress factors (improve nutrition, reduce inspections)
• Consider requeening with hygienic stock
• In some cases, shook swarm technique can help (transferring bees to new foundation)

Fungal Diseases

Chalkbrood

Chalkbrood, caused by the fungus Ascosphaera apis, thrives in cool, damp conditions. It’s often one of the first signs that a colony is experiencing stress.

How to Identify Chalkbrood:

• Mummified larvae that resemble white or gray chalk pieces
• Infected larvae are often found at the hive entrance or on the bottom board
• Brood pattern may be spotty but less so than with bacterial diseases
• Affected larvae are typically sealed, then uncapped by house bees

I remember consulting with a new beekeeper who panicked upon finding what looked like “pieces of rice” on their bottom board. After asking them to send photos, I confirmed it was chalkbrood and was able to recommend simple management changes that resolved the issue within weeks.

Prevention Techniques:

1. Maintain good hive ventilation to reduce moisture
2. Keep colonies in sunny locations when possible
3. Ensure adequate drainage beneath hives
4. Use screened bottom boards during warm months
5. Maintain strong colonies that can regulate temperature effectively

Management Strategies: There are no approved chemical treatments for chalkbrood, but fortunately, this disease often resolves with improved management:

• Remove and destroy affected frames in severe cases
• Replace old, dark comb with fresh foundation
• Consider requeening with hygienic stock bred to remove diseased larvae
• Ensure proper hive configuration for the season (appropriate entrances, ventilation)

Nosema

Nosema is actually two different microsporidian fungi: Nosema apis and Nosema ceranae. These fungi infect adult bee intestines, shortening their lifespan and reducing colony productivity.

How to Identify Nosema:

• Dysentery (brown streaking on the front of hives) with N. apis
• Gradual population decline without obvious symptoms with N. ceranae
• Poor spring buildup
• Queen supersedure at unusual times
• Reduced honey production

Nosema is tricky because confirmation requires microscopic examination of bee abdomens. I recommend sending samples to a lab if you suspect this disease.

Prevention Methods:

1. Maintain colonies with access to fresh water sources
2. Provide good ventilation to prevent condensation
3. Position hives to receive morning sun
4. Replace queens every 1-2 years
5. Replace old brood comb annually
6. Ensure colonies have access to diverse pollen sources

Treatment Options: Fumagilin-B was once the standard treatment but is no longer available in many regions. Alternative approaches include:

• Thymol-based products have shown some efficacy
• Supplementing with high-quality protein patties
• Applying heat treatments (keeping hives at 107°F for several hours) in controlled settings
• Using probiotics designed for honey bees (still being researched)

Viral Diseases

Deformed Wing Virus (DWV)

DWV has become increasingly prevalent as Varroa mites spread globally. The mites not only transmit the virus but suppress bee immunity, leading to clinical symptoms.

Visual Identification:

• Bees with shriveled, malformed wings
• Bees unable to fly, often crawling around the hive entrance
• Shortened abdomens
• Reduced lifespan of adult bees

Connection to Varroa Mites: I can’t emphasize this enough: controlling Varroa is the key to managing DWV. Over 90% of DWV cases are associated with Varroa infestations, so treating one without addressing the other is futile.

Prevention through Mite Control:

1. Monitor mite levels monthly using sticky boards, alcohol washes, or sugar rolls
2. Treat when mite levels exceed threshold (usually 2-3 mites per 100 bees)
3. Rotate treatment methods to prevent resistance
4. Consider breeding or purchasing Varroa-resistant stock
5. Use screened bottom boards to reduce mite populations

Colony Management for Affected Hives:

• Remove heavily infected bees (they won’t recover)
• Aggressively treat for Varroa using approved methods
• Consider requeening with hygienic stock
• Provide supplemental nutrition to boost immune function
• Reduce other stressors like poor ventilation or nutrition

Sacbrood Virus

Sacbrood virus affects larvae, causing symptoms that can be confused with bacterial brood diseases, though it’s generally less destructive.

Symptoms and Identification:

• Larvae fail to pupate and remain stretched out in their cells
• Affected larvae turn from pearly white to yellowish, then brown
• Infected larvae can be removed intact from cells (unlike AFB)
• Dead larvae dry into a characteristic “gondola-shaped” scale
• Perforated cappings as house bees attempt to remove infected larvae

Impact on Brood Development: Sacbrood typically affects only a small percentage of larvae and rarely kills colonies outright. However, it can weaken colonies enough to make them susceptible to other problems.

Prevention Strategies:

1. Maintain strong colonies with plenty of young nurse bees
2. Replace queens in affected colonies
3. Replace old brood comb regularly
4. Ensure good nutrition, especially protein from diverse pollen sources

Management of Infected Colonies:

• There are no chemical treatments specifically for sacbrood
• The disease often clears up on its own in strong colonies
• Requeen if the infection persists
• In severe cases, perform a shook swarm to move bees onto fresh comb

Parasitic Threats

Varroa Mites

I’ve been keeping bees long enough to remember the “before Varroa” days. These external parasites have completely transformed beekeeping practices worldwide.

Lifecycle and Reproduction: Varroa mites reproduce in capped brood cells, with a preference for drone brood. A female mite enters a cell before capping, lays eggs, and the offspring feed on the developing bee’s hemolymph (blood). When the bee emerges, the mites spread to other bees and the cycle continues.

Detection Methods:

1. Alcohol wash: Shake 300 bees in alcohol to dislodge mites (most accurate)
2. Sugar roll: Coat bees in powdered sugar to count dislodged mites (less destructive)
3. Sticky board: Place a greased board under screened bottom board (least accurate)
4. Visual inspection: Look for mites on adult bees or drone brood (unreliable until infestation is severe)

Integrated Pest Management Approaches: I’ve found that no single approach works for Varroa year after year. Instead, I use a combination of:

• Cultural controls (brood breaks, drone trapping)
• Mechanical controls (screened bottom boards, mite-resistant stock)
• Chemical controls (rotating treatments to prevent resistance)

Treatment Options:

• Synthetic chemicals: Apivar (amitraz), Apistan (fluvalinate), CheckMite+ (coumaphos)
• Organic acids: Formic acid (MAQS, Formic Pro), oxalic acid, hops beta acids
• Essential oils: Apiguard, ApiLife VAR (thymol-based products)
• Biotechnical: Drone brood removal, powdered sugar dusting, heat treatment

The key is timing treatments appropriately and monitoring effectiveness afterward.

Small Hive Beetle

Originally from sub-Saharan Africa, small hive beetles have become established pests in many regions with warm climates.

Identification and Lifecycle:

• Adult beetles are small (about 1/3 the size of a bee), dark, and quick-moving
• Larvae are white grubs that can be confused with wax moth larvae
• Eggs are laid in cracks and crevices throughout the hive
• Larvae feed on honey, pollen, and brood, causing honey to ferment and “slime out”

Prevention Strategies:

1. Maintain strong colonies that can patrol all areas of the hive
2. Use beetle traps inside hives (oil traps, corrugated plastic, etc.)
3. Keep hives in sunny locations (beetles prefer shade)
4. Maintain clean apiaries without excess equipment or debris
5. Extract honey promptly—don’t leave full supers sitting in warm conditions

Trapping Methods: I’ve had good success with various traps:

• Corrugated plastic strips (beetles hide in tunnels)
• Oil traps that fit between frames
• Bottom board traps with mineral oil
• CD case traps with apple cider vinegar bait

Soil Treatments for Pupae Control: Since beetles pupate in the soil, treating the ground around hives can break their lifecycle:

• Maintain dry, well-drained soil beneath hives
• Consider raising hives on stands with slippery legs
• In severe cases, approved soil drenches can reduce pupation success
• Beneficial nematodes can be applied to soil to kill pupating beetles

Seasonal Disease Prevention Calendar

I’ve found that thinking seasonally about bee health helps me stay ahead of problems. Here’s my approach throughout the year:

Spring Management Practices

• Perform thorough hive inspections as temperatures permit
• Look for signs of nosema and treat if necessary
• Begin Varroa monitoring early in the season
• Replace old, dark comb with fresh foundation
• Ensure colonies have adequate pollen for spring buildup
• Check for and clean up any deadouts before bees rob them

Summer Vigilance Techniques

• Monitor Varroa monthly and treat when thresholds are exceeded
• Watch for small hive beetles in southern regions
• Ensure adequate ventilation during hot weather
• Check brood patterns regularly for signs of disease
• Prevent robbing by reducing entrances during dearth periods
• Maintain water sources to prevent stress

Fall Preparation Strategies

• Treat for Varroa before winter bees are produced (usually August-September)
• Ensure colonies have enough healthy young bees for winter cluster
• Check for and address any brood bee diseases before winter
• Consolidate weaker colonies if necessary
• Reduce entrances to prevent robbing
• Ensure adequate honey stores for winter

Winter Health Monitoring

• Periodically check hive weight to monitor food consumption
• Listen for strong clusters on warmer winter days
• Clear dead bees from entrances to maintain ventilation
• Treat for Varroa during broodless periods if appropriate
• Plan spring management based on fall observations
• Order replacement queens or packages if needed

See More: 5 Do’s and 5 Don’ts of Beekeeping: How to Care for Bees the Right Way

Hive Management Best Practices

Over the years, I’ve developed some core practices that help keep bee diseases at bay:

Regular Inspection Protocols

I inspect my hives thoroughly at least once a month during the active season, looking specifically for:

• Quality of brood pattern (compact vs scattered)
• Signs of disease in open and capped brood
• Evidence of parasites (Varroa, small hive beetles)
• Queen performance and egg-laying pattern
• Adequate food stores and incoming resources

Equipment Sanitation

Disease prevention starts with clean equipment:

• Scrape and flame tool edges between hives
• Store equipment in a manner that prevents pest infestations
• Sterilize used equipment before introducing it to your apiary
• Consider dedicating separate tools for known problem hives

Comb Rotation and Replacement

Old, dark comb can harbor disease spores and chemical residues:

• Mark frames with the year they were drawn
• Replace 20-25% of your brood comb annually
• Move older comb to honey supers before retiring it
• Render old wax for candles or other non-bee uses

Record Keeping for Disease Tracking

I can’t stress enough how important good records are. For each hive, I track:

• Mite counts and treatment dates
• Signs of disease and interventions
• Queen age and performance
• Honey and pollen stores
• Colony temperament and productivity

This information helps me spot patterns and address issues before they become serious problems.

Building Bee Resilience

The ultimate goal isn’t just treating bee diseases but building colonies that resist them naturally.

Genetic Resistance Through Queen Selection

I’ve gradually shifted to more resistant stock by:

• Selecting queens from colonies that maintain low mite counts
• Purchasing VSH (Varroa Sensitive Hygiene) queens
• Supporting local queen breeders who select for disease resistance
• Occasionally allowing strong colonies to raise their own queens

Nutrition and Supplemental Feeding

Well-fed bees have stronger immune systems:

• Locate apiaries near diverse forage when possible
• Provide protein supplements during pollen dearths
• Ensure colonies never run short on carbohydrates
• Consider essential oil supplements that support gut health

Stress Reduction Techniques

Like humans, stressed bees get sick more easily:

• Avoid frequent, unnecessary inspections
• Prevent overheating by providing shade in hot climates
• Ensure adequate ventilation in all seasons
• Prevent robbing situations that spread disease

Creating Disease-Resistant Apiaries

I think of my apiary as an ecosystem:

• Maintain appropriate hive density for your area
• Quarantine new colonies before introducing them to your main apiary
• Consider the “clean break” of making splits to interrupt disease cycles
• Practice good neighbor beekeeping by managing bee diseases promptly

Conclusion: 8 Common Bee Diseases & How to Prevent Them

The most important lesson I’ve learned is that prevention is infinitely easier than cure. By implementing good management practices, maintaining strong colonies, and addressing issues promptly, we can significantly reduce disease incidence in our apiaries.

Remember that bees have been dealing with diseases for millions of years. Our job is not to eliminate all pathogens but to create conditions where our colonies can thrive despite these challenges.