Understanding Bee Diseases: A Global Guide for Beekeepers

Honey bees are vital pollinators for agriculture and ecosystems globally. Maintaining healthy bee colonies is crucial for food security and environmental sustainability. Unfortunately, honey bees are susceptible to a variety of diseases and pests that can weaken or destroy colonies. This guide provides a comprehensive overview of common bee diseases, their symptoms, prevention strategies, and treatment options for beekeepers around the world.

Why is Understanding Bee Diseases Important?

• Economic Impact: Bee diseases can lead to significant economic losses for beekeepers due to reduced honey production, colony mortality, and the cost of treatment.
• Pollination Services: Healthy bee colonies are essential for pollinating crops, contributing to food production and biodiversity. Disease outbreaks can impact pollination services and agricultural yields.
• Global Food Security: A decline in bee populations due to diseases can threaten global food security by reducing the availability of pollinated crops.
• Environmental Impact: Honey bees play a crucial role in maintaining healthy ecosystems. Disease-related colony losses can have cascading effects on plant communities and other wildlife.
• Spread and Mutation: Some bee diseases are highly contagious and can spread rapidly among colonies. Disease agents can also mutate and become more virulent, posing a greater threat to bee health.

Major Bee Diseases and Pests

Varroa Mites (Varroa destructor)

Varroa mites are external parasites that feed on honey bee hemolymph (blood). They weaken bees, transmit viruses, and can ultimately lead to colony collapse. Varroa mites are considered the most significant threat to honey bee health worldwide.

Symptoms of Varroa Mite Infestation:

• Visible mites on adult bees and brood.
• Deformed wings and legs in newly emerged bees.
• Reduced brood production.
• Weak and dwindling colony.
• Increased susceptibility to other diseases.

Prevention and Treatment of Varroa Mites:

• Regular Monitoring: Monitor mite levels regularly using methods such as sugar shake, alcohol wash, or sticky boards.
• Integrated Pest Management (IPM): Implement an IPM strategy that combines cultural practices, biotechnical methods, and chemical treatments.
• Biotechnical Methods: Use drone brood removal, screened bottom boards, or other biotechnical methods to reduce mite populations.
• Chemical Treatments: Apply approved miticides according to label instructions, rotating different active ingredients to prevent resistance. Examples include:
  • Synthetic acaricides: Amitraz (Apivar), Tau-fluvalinate (Apistan), Flumethrin (Bayvarol). Use these sparingly and follow local regulations.
  • Organic acids: Formic acid (Mite Away Quick Strips, Formic Pro), Oxalic acid (Api-Bioxal, oxalic acid vaporization).
  • Essential oils: Thymol (Apiguard, Api Life VAR).
• Resistant Bee Stocks: Use varroa-sensitive hygiene (VSH) or mite-biter bee stocks that exhibit natural resistance to varroa mites. These are available in many countries through queen breeders.

Nosema Disease (Nosema apis and Nosema ceranae)

Nosema is a fungal disease that affects the digestive system of honey bees. Nosema apis was the original species, but Nosema ceranae has become more prevalent and is often associated with colony decline.

Symptoms of Nosema Disease:

• Dysentery (diarrhea)
• Weak and sluggish bees
• Reduced honey production
• Increased winter mortality
• Abdominal swelling
• Bees crawling outside the hive

Prevention and Treatment of Nosema Disease:

• Good Hive Management: Maintain strong and healthy colonies with adequate food stores.
• Hygiene: Keep hives clean and well-ventilated.
• Fumagillin: Historically, fumagillin (Fumadil-B) was used to treat Nosema, but its availability is limited in many regions due to resistance and regulatory concerns. Check local regulations before using any treatment.
• Nutrition: Provide supplemental feeding with sugar syrup or protein patties to boost bee health.
• Sanitation: Disinfect hive equipment with acetic acid or bleach solution to kill Nosema spores.

American Foulbrood (AFB) (Paenibacillus larvae)

American Foulbrood (AFB) is a highly contagious bacterial disease that affects bee larvae. It is considered one of the most serious brood diseases and can lead to colony death. AFB is characterized by its highly resistant spores, which can survive for decades.

Symptoms of American Foulbrood:

• Spotty brood pattern
• Sunken and discolored brood cappings
• Ropey consistency of dead larvae (when a stick is inserted into the cell and withdrawn, the remains stretch out like a rope)
• Foul odor
• Scale formation on the bottom of cells

Prevention and Treatment of American Foulbrood:

• Regular Inspections: Inspect brood regularly for signs of AFB.
• Hygiene: Practice good hive hygiene and sanitation.
• Antibiotics: Antibiotics such as tylosin or oxytetracycline can be used to suppress AFB, but they do not eliminate the spores. Their use is regulated in many countries, and can mask the disease while contributing to antibiotic resistance. Therefore, antibiotics are not a long-term solution.
• Burning: The most effective method to eliminate AFB is to burn the infected colony and hive equipment to prevent the spread of spores.
• Irradiation: In some countries, hive equipment can be irradiated to kill AFB spores.
• Prevention is Key: Using small cell foundation, keeping strong colonies, and requeening regularly helps prevent outbreaks.

European Foulbrood (EFB) (Melissococcus plutonius)

European Foulbrood (EFB) is another bacterial disease that affects bee larvae. It is generally less virulent than AFB but can still weaken colonies and reduce honey production. Unlike AFB, EFB does not form spores.

Symptoms of European Foulbrood:

• Twisted or coiled larvae
• Discolored larvae (yellowish or brownish)
• Sour odor
• Melting or watery appearance of larvae
• Larvae die before capping

Prevention and Treatment of European Foulbrood:

• Good Hive Management: Maintain strong and healthy colonies with adequate food stores.
• Hygiene: Keep hives clean and well-ventilated.
• Requeening: Requeening with a disease-resistant queen can help the colony overcome EFB.
• Brood Breaks: Remove brood frames to create a brood break, which can disrupt the EFB cycle.
• Antibiotics: While antibiotics may be used in some regions, they are generally discouraged due to the potential for resistance.
• Shook Swarm: Perform a shook swarm to transfer bees to new, clean equipment and break the disease cycle.

Chalkbrood (Ascosphaera apis)

Chalkbrood is a fungal disease that affects bee larvae. Infected larvae become hardened and chalk-like, hence the name. It's more prevalent in damp conditions or stressed colonies.

Symptoms of Chalkbrood:

• Hard, white or grayish larvae (mummies)
• Mummies found in uncapped cells or on the hive floor
• Spotty brood pattern

Prevention and Treatment of Chalkbrood:

• Good Ventilation: Ensure proper hive ventilation to reduce humidity.
• Strong Colonies: Maintain strong and healthy colonies.
• Requeening: Requeening with a hygienic queen can help the colony remove infected larvae.
• Sunlight: Place hives in sunny locations.
• Hygiene: Remove and destroy infected frames.
• Calcium Hydroxide (Lime): Some beekeepers dust frames with calcium hydroxide (lime) but evidence of efficacy is limited.

Small Hive Beetle (SHB) (Aethina tumida)

The small hive beetle (SHB) is a pest that can damage honey bee colonies. SHB larvae tunnel through combs, causing fermentation and slime, which can lead to colony absconding. SHB is more problematic in warmer climates.

Symptoms of Small Hive Beetle Infestation:

• Beetles running around in the hive
• Slime and fermentation in combs
• Damaged combs
• Colony absconding

Prevention and Treatment of Small Hive Beetle:

• Hive Hygiene: Keep hives clean and free of debris.
• Strong Colonies: Maintain strong colonies that can defend themselves against SHB.
• Beetle Traps: Use beetle traps to capture and kill SHB. Examples include:
  • Oil traps (placed between frames).
  • Ground traps (placed beneath the hive).
• Soil Treatment: Treat the soil around the hive with beneficial nematodes to kill SHB larvae.
• Screened Bottom Boards: Screened bottom boards can help prevent SHB larvae from pupating in the soil.
• Proper Spacing: Avoid excessive space within the hive, as SHB thrives in empty areas.

Bee Viruses

Several viruses can affect honey bees, often transmitted by varroa mites. These viruses can weaken bees, reduce their lifespan, and contribute to colony collapse. Some of the most common bee viruses include Deformed Wing Virus (DWV), Acute Bee Paralysis Virus (ABPV), Chronic Bee Paralysis Virus (CBPV), and Sacbrood Virus (SBV).

Symptoms of Bee Virus Infections:

• Deformed wings (DWV)
• Paralysis (ABPV, CBPV)
• Trembling
• Reduced lifespan
• Spotty brood pattern (SBV)
• Hair loss

Prevention and Treatment of Bee Viruses:

• Varroa Mite Control: Effective varroa mite control is crucial to prevent the spread of viruses.
• Resistant Bees: Select bee stocks that are resistant to viruses.
• Good Nutrition: Provide bees with a balanced diet to boost their immune system.
• Hygiene: Practice good hive hygiene to reduce viral load.
• Requeening: Requeening with a healthy queen can improve the colony's overall health.

Colony Collapse Disorder (CCD)

Colony Collapse Disorder (CCD) is a complex phenomenon characterized by the sudden and unexplained loss of adult bees from a colony. The remaining bees are often healthy, but the colony is unable to sustain itself. The exact causes of CCD are still not fully understood, but contributing factors may include:

• Pesticide exposure (especially neonicotinoids)
• Varroa mites and associated viruses
• Malnutrition
• Stress
• Habitat loss
• Poor queen health
• Lack of genetic diversity

Prevention of Colony Collapse Disorder:

• Minimize Pesticide Exposure: Avoid using pesticides near bee colonies.
• Varroa Mite Control: Implement effective varroa mite control strategies.
• Provide Adequate Nutrition: Ensure bees have access to a diverse and abundant food supply.
• Reduce Stress: Minimize stress factors such as overcrowding, transportation, and frequent hive manipulations.
• Promote Genetic Diversity: Use diverse bee stocks and avoid inbreeding.
• Habitat Preservation: Support habitat preservation and restoration efforts to provide bees with forage resources.

General Prevention Strategies for Bee Diseases

• Regular Inspections: Inspect colonies regularly for signs of disease and pests. Early detection is crucial for effective management.
• Good Hive Hygiene: Keep hives clean and well-ventilated. Remove debris and dead bees regularly.
• Strong Colonies: Maintain strong and healthy colonies with adequate food stores.
• Quarantine New Colonies: Quarantine new colonies before introducing them to your apiary to prevent the spread of diseases.
• Avoid Sharing Equipment: Avoid sharing hive equipment between colonies to prevent cross-contamination.
• Proper Nutrition: Provide bees with a balanced diet of nectar and pollen. Supplement with sugar syrup or protein patties if necessary.
• Monitor Mite Levels: Regularly monitor varroa mite levels and implement control measures when necessary.
• Requeening Regularly: Requeen colonies regularly with healthy, disease-resistant queens.
• Use Disease-Resistant Bee Stocks: Select bee stocks that are resistant to common diseases.
• Promote Genetic Diversity: Maintain genetic diversity within your bee populations to increase their resilience to diseases.
• Attend Beekeeping Workshops and Conferences: Stay up-to-date on the latest information and best practices for bee health management.

Global Best Practices for Bee Health Management

Bee health management practices vary depending on local conditions, regulations, and bee races. However, some general best practices apply globally:

• Integrated Pest Management (IPM): IPM is a holistic approach to pest and disease management that combines cultural practices, biotechnical methods, and chemical treatments.
• Sustainable Beekeeping: Sustainable beekeeping practices focus on minimizing environmental impact and promoting bee health.
• Collaboration and Knowledge Sharing: Beekeepers should collaborate with researchers, extension specialists, and other beekeepers to share knowledge and best practices.
• Government Regulations and Support: Governments should implement regulations and provide support for bee health research, monitoring, and education.
• Public Awareness: Raising public awareness about the importance of bees and the threats they face can help promote bee-friendly practices. For example, campaigns encouraging planting pollinator-friendly plants have gained traction in countries like the United Kingdom and the United States.
• Research and Development: Continued research and development are needed to develop new and effective methods for preventing and treating bee diseases. For instance, researchers in Australia are actively studying bee viruses and developing diagnostic tools.

Conclusion

Understanding bee diseases is essential for beekeepers around the world. By implementing preventive measures, monitoring colonies regularly, and using appropriate treatment strategies, beekeepers can help maintain healthy bee colonies and contribute to food security and environmental sustainability. Continued research, collaboration, and public awareness are crucial for protecting these vital pollinators for generations to come. Staying informed and adapting to new challenges is key for responsible beekeeping in a changing world. From the Americas to Asia, beekeepers are facing similar threats, highlighting the importance of a unified, global effort to protect our bees.