A honey bee colony functions as a single organism where each bee’s survival relies on the others. Diseases afflicting any individual can severely disrupt the entire colony’s health. European foulbrood is one bacterial infection, caused by Melissococcus plutonius, that threatens honey bees worldwide across all beekeeping regions. This guide focuses on approaches for the treatment and management of European foulbrood and examines its impact on hive products such as honey.
Detecting European foulbrood infection in a colony is straightforward due to characteristic symptoms. Observant beekeepers may also identify signs by examining the condition of the hive. Once symptoms suggest the disease, it is essential to confirm the diagnosis.
Obtaining a laboratory analysis is crucial for confirming or ruling out European foulbrood, ensuring accurate identification of the problem affecting your apiary. This is vital since other diseases, pests, or parasites might cause similar symptoms that could be confused with EFB.
European foulbrood specifically infects the brood, leading to a gradual decline in colony numbers. The main signs to look for include:
- brood patterns that appear uneven or patchy;
- discolored larvae along with dead larvae found in uncapped brood cells;
- presence of dead larvae within capped brood cells;
- and a distinct ammonia-like odor emanating from the hive.
Recognizing Symptoms of European Foulbrood
These symptoms should be your primary focus during hive inspections as they indicate potential European foulbrood infection. A thorough examination of any colony showing one or more signs is essential. Early detection is critical to halting the disease’s progression. The presence of an ammonia smell suggests the infection has spread extensively within the colony. Additional signs to help confirm Melissococcus plutonius infection include:
1. Altered Larvae Positioning
Infected larvae often assume unusual positions such as twisted or coiled shapes within their brood cells, diverging from the typical C-shape where a healthy larva’s head points upward near the cell opening.
2. Color Alterations in Dead Larvae
Larvae killed by European foulbrood frequently undergo color changes, starting from their normal pearly white shade to yellow, then progressing to deeper browns or black, sometimes becoming a liquefied mass. When larvae reach this stage, the ‘Ropiness’ test can be applied for diagnosis.
3. Color Changes in Larval Tracheae
Early infection stages can also be detected by examining the larval tracheae, which typically turn vivid yellow in infected specimens.
4. Desiccated Larvae
After death, larvae affected by European foulbrood remain gooey for some time before drying out, turning dark brown or black and forming rubbery scales lightly attached to the brood cell walls. These scales produce spores, aiding disease persistence and risking re-infection despite treatment efforts.
Diagnosing European Foulbrood
Beekeepers should conduct detailed hive inspections at least twice yearly, ideally in spring and fall when EFB is more prevalent. However, vigilance throughout the year remains important, as European foulbrood can emerge at any time.
Colonies experiencing stressful situations—such as swarming, attacks from pests, parasites, diseases, or frequent hive opening—are more susceptible to infection. Monitoring should be intensified following such events.
When inspecting for European foulbrood, carefully examine every brood frame and cell. Removing bees by gently brushing helps in inspecting both sides of frames fully. Look out for all signs related to EFB during this process.
Noticing irregular or patchy brood patterns, dead brood, or unusual brood coloration warrants concern and further investigation, including seeking expert advice or conducting additional diagnostic measures.
Ropiness Test for Diagnosing European Foulbrood
The ‘Ropiness’ test is a practical field method to differentiate European foulbrood from other diseases such as American foulbrood, which can present with similar dead larvae. European foulbrood typically causes larvae to twist and die before capping, whereas American foulbrood kills larvae mostly after cell capping and does not produce twisted larvae. However, EFB occasionally fails to destroy all larvae before capping.
Another distinction lies in the texture of dead brood remnants: EFB-infected remains are rubbery and loosely attached to brood cells, while American foulbrood results in brittle, firmly attached residues.
Performing the Ropiness Test
The Ropiness test is conducted by inserting a matchstick or toothpick into a deceased brood suspected of European foulbrood infection, then slowly withdrawing it to observe the consistency of the resulting gooey substance. This sticky material stretches into a thread, which breaks as the stick is pulled further from the brood cell. This method aids beekeepers in differentiating European foulbrood from American foulbrood, as European foulbrood typically produces a short and thick thread, whereas American foulbrood results in a longer, thinner thread.
Interpreting Ropiness Test Outcomes
In European foulbrood cases, the thread created by the test usually measures around 1.5 centimeters. If the thread stretches to between 3 and 5 centimeters, it may suggest the presence of American foulbrood instead.
The bacterium Paenibacillus Alvei acts as a secondary, opportunistic pathogen that often appears alongside Melissococcus Plutonius. Its presence in a European foulbrood-infected brood can alter the typical consistency of the liquefied larvae mass, making it less cohesive. This change can cause the mass to form longer threads during the Ropiness test, potentially leading to a false identification of American foulbrood. To avoid such misdiagnoses, it is important to consider other distinguishing symptoms of European foulbrood when interpreting test results.
If the Ropiness test fails to provide a definitive diagnosis or remains unclear despite other symptom assessments, then sending samples for laboratory analysis is recommended.
Confirming European Foulbrood via Laboratory Testing
Samples taken from suspected infected beehives must be carefully collected, stored, and transported to laboratories to avoid contamination. Both novice and experienced beekeepers are able to gather and submit well-preserved samples for accurate laboratory diagnosis of European foulbrood.
Utilizing protective gear, securely sealing samples, employing cushioned packaging, and ensuring prompt delivery have enabled many beekeepers to successfully diagnose European foulbrood and other honey bee diseases. Early detection is crucial, as it permits the initiation of control measures in time to potentially save an at-risk colony.
Managing and Treating European Foulbrood
European foulbrood is a disease that, in many regions, must be reported to authorities. Even in places where reporting is not mandatory, informing other beekeepers about local outbreaks is advisable. The disease typically spreads slowly between hives unless incidents like drifting or robbing allow infected bees to enter new colonies.
Transmission can also occur during routine apiary activities, primarily through contact with nurse bees and larvae. Treatments exist to help mitigate the impact of infection on the colony, which we will explore further.
After reducing the disease’s impact on your bees, the ultimate goal is to eradicate it from the hive. Various strategies and therapies are available for European foulbrood, with an emphasis on prevention as the best approach. Nonetheless, most beekeepers will encounter this disease at some point, so being informed about effective responses is essential.
Applying diligent apiary, hive, and colony management techniques is vital to minimizing the incidence of European foulbrood. When an infection emerges in a single hive, effective management practices can help contain and eventually eliminate the disease within the entire apiary.
1. Antibiotic Use
Antibiotics have long been employed to treat European foulbrood, though the pathogen has shown the capacity to develop resistance to several drugs. Terramycin is one of the few antibiotics tested extensively and remains the only one approved by the FDA for treating European foulbrood in honey bees. However, using Terramycin is a control method available to individual beekeepers and does not eradicate the disease completely. It suppresses symptoms long enough to relieve stress on the colony, but once treatment stops, bacterial spores may germinate anew.
Applying Terramycin slows bacterial spore germination, protecting larvae from harm while allowing worker bees to remove dead brood. Although symptoms may cease during treatment, beekeepers should not become complacent, as antibiotics form just one part of chemical-based disease management strategies to keep European foulbrood under control.
2. Chemical Sanitation Practices
Using chemicals to disinfect equipment is a viable option in managing European foulbrood. It’s standard practice to thoroughly clean tools and interchangeable hive parts before using them in different hives to prevent disease spread. Solutions such as washing soda and bleach are effective for washing, wiping, or dipping equipment and hive components to sanitize them properly.
3. Reducing Disease Spread via Hive Components
Langstroth hives, common among beekeepers, consist of multiple parts that can be swapped between colonies of matching sizes. Minimizing such interchange helps reduce disease transmission risks, and when necessary, the use of sanitizing solutions is crucial. Many beekeepers routinely boil frames to extract wax and cleanse them thoroughly; the heat exposure combined with proper storage effectively controls honey bee diseases.
Scorching is another sanitation technique applied to hive parts, tools, and equipment. Following European foulbrood outbreaks, scorching is advised if the entire hive and colony are not to be destroyed by burning.
4. Selective Breeding of Honey Bees
Breeding honey bees with stronger hygienic behaviors offers a promising approach to combating European foulbrood. Some bees demonstrate heightened abilities to detect and remove diseased larvae, potentially limiting infection spread. However, this behavior can inadvertently facilitate transmission within the hive, as worker bees handling dead larvae may become infected and pass the pathogen to healthy larvae.
5. Apiary and Hive Management
The barrier management approach is an effective disease control strategy for apiaries of any size. It involves dividing beehives into distinct groups that are managed uniformly, ensuring that equipment stays within its designated group and is not transferred between groups. This containment minimizes the spread of diseases, restricting any outbreak to a single group at most. Many beekeepers have successfully preserved their apiaries from devastating bee diseases by implementing this system, which proves particularly useful in controlling European foulbrood.
High-quality hive management is crucial in preventing European foulbrood outbreaks. Research indicates that low temperatures make bee larvae more vulnerable to infection by Melissococcus Plutonius, especially those situated near the edges of honeycomb where cold spots develop. The disease strikes before larvae begin pupation, making early-stage brood particularly at risk. During winter, decreasing the size of brood chambers helps reduce cold-exposed brood, thereby lowering the chances of a European foulbrood attack, which can fatally weaken colonies before spring.
6. Periodic Removal and Replacement of Comb in Hives
It is recommended to cycle out and replace old comb in your hives every three to four years because aged comb often harbors disease agents. Leftover larvae remnants trapped in old comb can release pathogens, making it a hidden source of infection. Many beekeepers prefer to extract such comb for beeswax processing, especially when the brood comb has been used extensively.
Rather than removing all old comb simultaneously, some beekeepers opt for a gradual replacement by periodically introducing fresh, undrawn frames into the brood chamber, encouraging bees to build new comb over time.
Comb that has darkened to brown or black should be taken out of the brood area and can be reassigned for storing honey. Although some beekeepers favor darker comb in brood chambers for the contrast it provides when identifying white larvae, it is important not to allow comb to age excessively within the hive to prevent disease buildup.
European Foulbrood Treatment with Terramycin
Terramycin, also known as Oxytetracycline, is an antibiotic commonly used to treat both American and European foulbrood in honey bees. This treatment alleviates disease pressure and can save a colony from being destroyed. After symptoms diminish or disappear following treatment, it is essential to thoroughly sterilize, scorch, or burn the infected hive before transferring the colony to a clean hive. Close monitoring for any signs of relapse is necessary once the bees are relocated.
Considerations Before Using Terramycin in Beekeeping
While Terramycin offers benefits in managing European foulbrood, its drawbacks and potential side effects must be carefully weighed alongside alternative control measures. Prompt action using the most effective available method is vital once the disease is detected to minimize colony losses.
Several concerns and limitations accompany the use of Terramycin or similar antibiotics to combat honey bee diseases like European foulbrood, including but not limited to:
- Terramycin requires continuous application to prevent spores of Melissococcus Plutonius from germinating in healthy larvae and to inhibit bacterial growth in infected larvae. Its efficacy depends on strict adherence to proper management and dosing instructions.
- Exposure to sunlight degrades Terramycin, reducing its potency.
- Terramycin cannot be incorporated into hot food preparations that are later fed to bees, as heat deactivates the antibiotic.
- Legal regulations prohibit using Terramycin during honey flow periods or in hives with honey supers unless those supers are removed, since residues can persist in harvested honey.
- For effective treatment, the colony must have an adequate population of nurse bees to ensure proper distribution and uptake of the antibiotic.
Does European Foulbrood Impact Honey?
European foulbrood specifically targets bee brood and does not directly alter honey quality. However, treatments used to control the disease can influence honey’s taste, color, and overall quality. Additionally, weakened colonies due to the disease often produce lower honey yields and fewer hive products.
Conclusion
Bee diseases pose significant challenges for beekeepers, but prevention is achievable regardless of operation size or experience level. European foulbrood represents one of the most destructive bacterial afflictions in honey bees and managing it requires considerable effort, resources, and time.
When preventative strategies fail and European foulbrood affects your hives, applying the information provided in this guide can help you manage and control the disease effectively. Employing these recommendations supports successful treatment and better apiary health.
References
- https://edis.ifas.ufl.edu/publication/IN1272
- https://www.nature.com/articles/s41598-022-09796-4
- https://bee-health.extension.org/european-foulbrood-a-bacterial-disease-affecting-honey-bee-brood/
- https://www.mass.gov/doc/european-foulbrood-fact-sheet/download
- https://honeybeehealthcoalition.org/wp-content/uploads/2019/06/HBHC__AFB-EFB-Final-061119.pdf
- https://nationalbeeunit.com/public/beekeepingFaqs/europeanFoulbroodEfb.cfm
Have your beehives ever been afflicted by the European foulbrood disease? Leave a comment below and let us know what your experience was like.
Source: European Foulbrood Treatment and Management – BeeKeepClub (beekeepclub.com)