Honeybees play a critical role in pollinating crops and maintaining a healthy ecosystem. Unfortunately, they face a range of diseases that can weaken hives, reduce honey production, and even cause colony collapse if left untreated. Understanding the most common bee diseases and how beekeepers prevent them can help you protect these vital pollinators. 

Below are the most common diseases affecting honeybees and the practical steps beekeepers take to keep their hives healthy. 

1. American Foulbrood (AFB)

American Foulbrood is one of the most serious bacterial infections that can affect honeybees. It attacks developing larvae, leaves a sticky mass in cells, and produces long-lasting spores that can survive for decades. AFB is also highly contagious. 

Signs to watch for:

• Patchy brood pattern
• Sucken, darkened brood caps
• A strong, unpleasant odor
• Larvae that turn brown and sticky 
• Brown, snot-like ropes in dead larvae 

Prevention methods:

• Regular hive inspections
• Checking brood combs in the spring or autumn for early signs of AFB
• Avoiding the reuse of contaminated equipment
• Purchasing bees from reputable, inspected sources 
• Promptly removing and destroying infected frames when detected

2. European Foulbrood (EFB)

European foulbrood is a bacterial disease that affects larvae before they are capped. Unlike AFB, it doesn’t form long-living spores and is often linked to stress or poor nutrition. EFB typically manifests in the spring. 

Signs to watch for:

• Twisted or melted larvae
• Yellowish or gray larvae color
• Spotty or uneven brood pattern
• Strong sour odor

Prevention methods: 

• Ensuring colonies have adequate nutrition
• Checking brood combs in the spring or autumn for early signs of EFB 
• Requeening with strong, healthy queens
• Maintaining proper hive ventilation
• Avoiding practices that lead to the loss of heat in the hive
• Reducing stress caused by overcrowding or poor forage

3. Chalkbrood

Chalkbrood is a fungal disease that causes larvae to harden into white, chalk-like mummies, often seen at the hive entrance. It often results from high stress or temperature changes in the hive. It is most common in the spring, when it’s cooler, and the hive is rapidly growing. 

Signs to watch for:

• White or gray mummiers in or near the hive
• Weak brood development
• A rattling sound when shaking a comb

Prevention methods:

• Improving hive ventilation
• Replacing old or damp combs
• Keeping hives dry and well-positioned 
• Selecting hygienic bee strains resistant to fungal diseases

4. Nosema

Nosema is a microscopic parasite that infects adult bees, invading their gut, affecting their digestive systems, causing weakness, and shortening their lifespan. Since it’s invisible to the naked eye and causes very general symptoms, it’s commonly referred to as the “silent killer” of bees. 

Even though it often goes undetected, you may still catch it by watching for: 

• Reduced colony population
• Poor honey production
• Dysentery stains near the hive

Prevention methods:

• Keeping hives clean and dry
• Replacing old comb regularly
• Proving proper winter nutrition
• Reducing stress during seasonal transitions

5. Deformed Wing Virus (DWV)

Deformed Wing Virus is commonly spread by Varroa mites and results in bees with misshapen wings that cannot fly or forage. 

Signs to watch for:

• Bees with crumpled or shortened wings
• Reduced foraging activity
• Rapid colony decline 

Prevention Methods: 

• Effective Varroa mite management
• Regular monitoring of mite levels
• Using integrated pest management (IPM) strategies
• Avoiding untreated infestations 

The Role of Varroa Mites in Bee Disease

One of the biggest threats honeybees face isn’t disease but the Varroa destructor mite. These tiny external parasites attach to bees and feed on their fat bodies (a critical organ for immunity and nutrient storage). 

These mites are dangerous because:

• They weaken bees’ immune systems
• They spread viruses like Deformed Wing Virus (DWV)
• High mite loads can collapse a colony in a single season

Beekeepers routinely monitor mite levels using sugar rolls, alcohol washes, or sticky boards and treat colonies when they reach the threshold. Integrated Pest Management (IPM) methods include organic acids, essential oils, drone brood removal, and carefully timed treatments.

General Disease Prevention Best Practices

While individual diseases require specific responses, successful beekeepers prevent most sickness by:

• Conducting routine hive inspections
• Cleaning hive tools and gloves to prevent cross-contamination 
• Maintaining strong, well-fed colonies
• Practicing good hive hygiene
• Adopting a barrier management system 
• Replacing old equipment and honeycomb every three to five years
• Monitoring for pests
• Choosing disease-resistant bee stocks when possible

Healthy bees are better equipped to fight disease naturally. 

Help Bee Colonies Thrive 

Bee diseases pose a serious challenge, but they are not unbeatable. With proper education, attentive hive management, and early intervention, beekeepers can dramatically reduce the impact of disease on their colonies. Preventive care not only protects individuals but also helps support pollination, biodiversity, and food systems worldwide.