Bees play a foundational role in natural ecosystems and agriculture. Their pollination services are integral to the reproduction of many plants, including a significant portion of human food. Bee colonies can encounter various health challenges, from parasitic infestations to bacterial and fungal diseases. Understanding these threats and implementing management strategies is important for maintaining bee health and supporting their populations.
Addressing Pests Affecting Bee Colonies
The Varroa mite, Varroa destructor, is a concerning threat to bee colonies. These external parasites attach to adult bees and developing brood, feeding on their hemolymph and fat body tissue. This weakens bees, leading to deformed wings and a reduced lifespan. Varroa mites also transmit various viruses, further compromising colony health. Mite presence is identified through visual inspection, powdered sugar rolls, or alcohol washes.
Treatment involves a combination of methods. Chemical treatments (miticides) include Apivar (amitraz), oxalic acid, and formic acid. Oxalic acid is effective against mites on adult bees, especially during broodless periods, applied through dribbling or vaporization. Formic acid penetrates capped brood cells to kill mites within.
Cultural methods also contribute to mite management, such as drone brood removal or screened bottom boards. Integrated pest management (IPM) combines these approaches to minimize reliance on any single method, promoting long-term colony resilience.
Small hive beetles, Aethina tumida, originally from sub-Saharan Africa, are a significant pest, particularly in stressed or weakened colonies. Adult beetles and their larvae consume honey, pollen, and bee brood, causing honey to ferment and slime out the hive, rendering it unusable. Beekeepers identify infestations by observing adult beetles scurrying on combs or finding slimed honey and tunneling larvae.
Management focuses on sanitation and maintaining strong colonies. Keeping the apiary and honey house clean, and extracting honey supers quickly after removal from the hive, helps reduce attractants. Freezing infested comb at -12°C (10°F) for 24 hours kills all beetle life stages. In-hive traps, often filled with vegetable oil, can be placed within the hive to drown adult beetles as bees chase them. Some traps replace the bottom board with a screen over an oil tray, allowing beetles to fall through and drown.
Wax moths (Galleria mellonella, Achrois grisella) are scavengers that thrive in weak colonies or on stored comb. Their larvae tunnel through wax, leaving behind silken webs and debris, and can destroy combs within 10-15 days in warm climates. Strong colonies generally deter wax moths, but unattended or stored combs are highly vulnerable.
Control measures involve maintaining robust colonies that can actively defend their combs. Reducing the hive entrance for weak colonies and regularly cleaning bottom boards to remove debris can help. For stored combs, freezing them at 0 to -10°C (32 to 14°F) for at least 5 hours effectively kills all life stages. Chemical fumigants like sulfur powder or acetic acid can also be used for stored combs, though proper ventilation is necessary due to their toxicity.
Managing Bee Diseases
American Foulbrood (AFB), caused by the spore-forming bacterium Paenibacillus larvae, is a destructive honey bee brood disease. Infected larvae consume spores, which germinate in their gut, leading to their death, typically after the cell is capped. Symptoms include a spotty or irregular brood pattern, sunken and greasy-looking capped cells, and a foul odor from the rotting larvae. A characteristic symptom is the “ropy” consistency of dead larvae, which stretches like a string when probed.
AFB spores are resilient and can remain viable in wax and honey for decades. Due to its contagious nature and persistence, burning infected hives and equipment is often the most effective measure to prevent further spread. In some regions, antibiotics like oxytetracycline (Terramycin) or tylosin may be used for prevention or in minor cases, though they do not kill the spores and can lead to resistance. These treatments typically require a veterinary prescription.
European Foulbrood (EFB), caused by the non-spore-forming bacterium Melissococcus plutonius, affects young larvae before their cells are capped. While less severe than AFB, EFB can still significantly weaken a colony. Infected larvae change color from pearly white to yellow-brown, may appear twisted or curled, and can have a sour odor. Unlike AFB, the larval remains are often soft and easily removed from the cell.
Management of EFB involves improving colony conditions. Mild infections may resolve on their own during a strong nectar flow. Requeening with a young, healthy queen can break the brood cycle and allow nurse bees to clean out diseased larvae. Shaking adult bees onto new, clean comb and disposing of the old comb is another intervention. Antibiotics, such as oxytetracycline, can be used to treat EFB, often administered in sugar syrup, but their use requires a veterinary prescription.
Nosema disease, caused by microsporidian parasites Nosema apis or Nosema ceranae, primarily affects adult bees. Spores are ingested and replicate in the bee’s midgut, damaging intestinal cells and leading to dysentery, reduced lifespan, and impaired foraging. Infected colonies may not show obvious external symptoms until the population significantly declines.
Treatment for Nosema involves supporting bee health through good nutrition and proper hive ventilation. Fumagillin, an antibiotic, has historically been used to control Nosema by reducing spore production, though it does not kill the spores themselves. Its availability and use may be restricted.
Chalkbrood is a fungal disease caused by Ascosphaera apis that infects honey bee larvae. Larvae consume fungal spores, which germinate in their gut, consuming their body tissues and leading to death. The infected larvae become swollen and eventually dry out into hard, chalk-like “mummies” that can be white, grey, or black. These mummies are often found on the bottom board or at the hive entrance as bees attempt to remove them.
No registered chemical treatments exist for chalkbrood. Management strategies focus on promoting strong, hygienic colonies that can naturally remove infected larvae. Improving hive ventilation and ensuring a warm, dry environment can help, as the fungus thrives in cool, damp conditions. Requeening with a queen from a more hygienic or resistant stock can also enhance a colony’s ability to cope with chalkbrood. Regularly replacing old brood comb can also reduce the fungal load within the hive.
Supporting Bee Health Through Nutrition and Environment
Adequate nutrition is foundational for bee health, influencing immune response and overall resilience against pests and diseases. Bees require diverse sources of pollen for protein, amino acids, lipids, and vitamins, and nectar for carbohydrates. During periods of nectar or pollen scarcity, such as droughts or cold weather, supplemental feeding can support colony strength. Sugar syrup provides carbohydrates, while pollen patties or protein-rich substitutes offer necessary protein. Clean water access is also important year-round for temperature regulation and honey processing.
Pesticide exposure poses a significant threat. Even low-dose chronic exposure can weaken colonies and make them more susceptible to diseases. To minimize risk, avoiding pesticide applications directly on flowering crops or other blooming plants where bees forage is recommended. Applying pesticides in the late evening or early morning, when bees are less active, can reduce direct contact. Choosing less toxic formulations and avoiding tank mixes of different pesticide classes can also help. Communicating with local beekeepers about planned applications allows them to take protective measures, such as temporarily moving or confining hives.
Creating pollinator-friendly habitats provides bees with essential food and nesting resources. This involves planting a diverse array of native, nectar- and pollen-rich flowers that bloom throughout the growing season. Reducing habitat fragmentation and providing undisturbed areas for nesting are also beneficial. Many native bee species nest underground, while others are cavity nesters, utilizing hollow plant stems or holes in dead wood. Leaving some areas of undisturbed soil, brush piles, and dead wood can provide suitable nesting sites.
Good beekeeping practices are integral to maintaining robust bee populations and reducing reactive treatments. Regular hive inspections allow beekeepers to monitor colony health, identify issues early, and ensure adequate space for growth. Proper ventilation within the hive helps manage moisture and temperature, creating a healthier environment. Managing hive population by preventing overcrowding and requeening with young, productive queens contributes to overall colony vigor and disease resistance.