Honey bee colonies face threats from various fungal pathogens. Spores from fungi like chalkbrood, stonebrood, and nosema can infiltrate hives and wreak havoc if not controlled. Infected bees exhibit symptoms like body discoloration, odd postures, lethargy, and dysentery before dying. Left unchecked, fungi can decimate bee populations, weaken colonies, and severely impact honey production.
How do bees encounter harmful fungi?
Bees contract harmful fungi primarily through exposure to contaminated pollen during foraging. Additionally, they can pick up fungi through infected bees, poor hive hygiene, or from materials introduced by beekeepers. Interactions with bees from other colonies, such as drifting or robbing, can also introduce fungal contaminants into a hive.
Old brood comb and hive materials enable spores to persist for years. Reusing equipment, frames, and foundations without proper sterilization propagates the spread between colonies.
Stress is a factor in fungal outbreaks. Varroa mite infestations, pesticide exposure, poor nutrition, cool damp conditions, overcrowding, and transportation stress impair bees’ immune defenses. With weakened immunity, fungal spores easily take hold and proliferate.
Fungal diseases in honey bees
Chalkbrood and stonebrood
Caused by Ascosphaera apis, chalkbrood manifests as hard, white larvae that resemble small mummies. Infected larvae often display an arched, shrimp-like posture. Darkened larvae may emit a sulfurous stench. While rarely fatal alone, chalkbrood can stress and weaken colonies over time. Cool, damp conditions encourage growth.
Stonebrood arises from a combination of Aspergillus types. Infected larvae turn tough and stone-like with a greenish tint. The fungus has a moldy, musty odor and spreads rapidly. As with chalkbrood, stonebrood is more apt to weaken rather than destroy colonies. Proper hive ventilation inhibits its growth.
Nosema
Nosema, caused by the fungi Nosema apis and Nosema ceranae, is a significant concern for beekeepers as it primarily targets adult bees, leaving the larvae unharmed. Affected bees exhibit noticeable changes in their behavior and appearance. They often appear sluggish and may have a swollen appearance, with their bodies taking on a greasy or wet sheen. This is a direct result of the fungus damaging their gut tissue.
As the disease progresses, the behavior of the bees becomes increasingly erratic. Instead of maintaining their usual cleanliness, infected bees begin to defecate in and near the entrance of the hive, which is highly abnormal and a clear sign of distress. In the advanced stages of the infection, bees can be observed trembling and crawling aimlessly around the hive entrance before dying. Nosema is primarily transmitted primary through contact with the feces of infected bees.
Preventing and treating honey bee fungal infections
Strong colonies with an abundance of nurse bees to tend the brood have greater resilience against fungal diseases. Ensuring bees have diverse nutrition across the seasons bolsters immunity and limiting stressors, allowing adequate space, and proper ventilation also inhibits fungal growth.
To protect bees from fungal diseases, beekeepers employ a multi-faceted strategy, which includes regularly replacing older parts of the hive where baby bees develop to reduce spore buildup, removing heavily diseased hives, and thoroughly cleaning all beekeeping tools
Once a fungal infection has taken hold, beekeepers can use a mix of traditional and modern treatments stop the spread. Essential oils, such as thymol (from thyme) and lemongrass oil, have natural antifungal properties and are mixed into food or applied directly to the hive structure in a water solution. Additionally, beekeepers might use specific antibiotics designed to target and eliminate the fungal pathogens.
While treatment can help once an outbreak starts, prevention is ideal. Maintaining healthy colonies with access to clean food and water gives bees natural resistance. Careful inspection for symptoms and prompt action allows beekeepers to control fungal pathogens and reduce their harm.
Vigilance fights fungus
Fungal pathogens require continued vigilance and rapid response when detected. Diseases like chalkbrood can persist in abandoned equipment or feral colonies for years, posing a risk for commercial operations.
Advancements in fungal treatments, bee stock breeding, and management strategies offer hope. But day-to-day monitoring, hygienic practices, strong nutrition, low-stress conditions, and prompt intervention by beekeepers when issues arise remain paramount.
