Apr 5, 2026
14.3 Adult Bee Diseases.
Nosema and Deformed Wing Virus affect adult bees in different ways, yet both reduce the strength and resilience of the colony. Nosema works quietly within the digestive system, while DWV shows visible deformities linked to Varroa mites. By observing behaviour, population trends, and physical signs, a beekeeper can begin to recognise these conditions. The aim is not immediate certainty, but steady awareness that supports timely and thoughtful action.
Understanding Nosema Disease
Nosema is a widespread adult bee disease caused by microscopic, spore-forming organisms that invade the digestive tract. These microsporidian parasites multiply rapidly inside the epithelial cells lining the true stomach of the honey bee. This internal invasion severely limits the bee's ability to digest pollen and absorb vital nutrients. For a beginner, the key point is that this infection takes place entirely out of sight. This hidden development makes the disease difficult to detect during standard hive evaluations.
The physical toll of the disease significantly shortens the lifespan of individual worker bees. Because their bodies cannot process proteins efficiently, infected nurse bees stop producing royal jelly prematurely. This nutritional breakdown reduces their capacity to feed the queen and support the emerging larvae. In practice, this means the overall population of the colony will begin to dwindle unexpectedly. Over time, you will begin to recognise this slow decline as a major threat to spring development.
An infected colony frequently exhibits clear signs of dysentery along the exterior of the hive equipment. This problem occurs when bees are confined inside for long periods during cold or wet weather. You will notice distinct yellow or brown streaks of faecal matter staining the front wall and landing board. This staining happens because the microsporidia irritate the gut lining and cause a severe build-up of waste material. For a beginner, the key point is to watch for these external markings during early spring walks.
The definitive diagnosis of Nosema cannot be made through visual signs alone. Beekeepers must collect a sample of older foraging bees and send them to a laboratory for microscopic examination. Technicians will crush the digestive tracts to count the presence of the distinctive oval spores under a high-power lens. In practice, this means you should consider sampling if a hive shows a slow spring build-up despite having a productive queen. This methodical step replaces guesswork with clear, verifiable evidence.
Recognising Deformed Wing Virus
Deformed Wing Virus is a destructive viral pathogen that impacts the physical structure of developing honey bees. This virus remains largely harmless at low levels until it finds a vector to accelerate its spread. The parasitic Varroa mite acts as this primary vector by transmitting the virus directly into the bloodstream of pupae and adults. For a beginner, the key point is that the virus and the mite operate as a single combined health threat. This strong connection means that managing mite counts is the only way to control the virus.
Adult bees infected with high levels of the virus during their pupal growth display unmistakable physical deformities. They emerge from their wax cells with shrivelled, short, or completely missing wings that resemble small threads. Their abdomens frequently appear stunted, rounded, and significantly smaller than those of their healthy sisters. In practice, this means these compromised individuals are completely unable to fly or perform routine tasks. Over time, you will begin to recognise these damaged bees crawling aimlessly on the bottom board.
The presence of visually deformed bees indicates that the virus has already reached a critical threshold inside the colony. These damaged workers are quickly dragged out of the brood nest and discarded outside by the house cleaners. You may find small groups of these flightless bees trembling or climbing blades of grass near the entrance. For a beginner, the key point is to check the ground around your stands during every visit. This habit naturally leads to an early assessment of internal viral pressure.
Unchecked viral progression leads directly to a condition known as parasitic mite syndrome. This advanced state causes a complete breakdown of the colony's social organisation and brood-rearing cycle. The worker population drops sharply, the bees become highly agitated, and the remaining brood pattern turns extremely spotty. In practice, this means the colony will eventually collapse or abscond from the box entirely. This tragic outcome highlights the necessity of keeping your Varroa populations low throughout the year.
Managing Adult Diseases Through Hive Hygiene
Supporting the colony against adult bee diseases requires a strong focus on nutrition and equipment sanitation. Nutritional stress leaves bees highly vulnerable to both Nosema infections and viral multiplication. Beekeepers can assist their colonies by positioning yards in locations with access to diverse, high-quality pollen sources. This abundant protein allows the bees to rebuild their fat bodies and maintain robust immune responses. This natural strength serves as the primary barrier against seasonal pathogens.
In practice, this means you must keep the interior of your hives completely dry and properly ventilated. High humidity inside the brood chamber creates an ideal environment for fungal and microsporidian spores to persist. You can reduce this moisture by using screened bottom boards or providing a small top entrance for airflow. Never allow bees to consume fermented honey stores, as this material damages their digestive tracts. This steady attention to environmental conditions keeps your stock healthy and productive.
Strict equipment hygiene is equally vital to prevent the transfer of pathogens between different colonies. You should routinely clean your hive tool with alcohol or heat it with a pocket torch between inspections. Avoid swapping frames of honey or brood from a weak, failing hive into a strong, healthy one. If a colony dies from a suspected pathogen, close the entrance immediately to prevent robbing bees from carrying contaminated resources away. This disciplined approach protects your entire apiary from preventable losses.
Summary
Adult bee diseases like Nosema and Deformed Wing Virus significantly reduce colony longevity and overall productivity. Nosema is an internal digestive disorder caused by microsporidian parasites, often manifesting as external faecal staining and a slow population decline. Deformed Wing Virus is a viral infection vectored by Varroa mites, resulting in adult bees emerging with shrivelled wings and stunted bodies. Both conditions are heavily exacerbated by seasonal and environmental stress. Beekeepers can mitigate these risks by ensuring access to diverse pollen sources, improving hive ventilation, and maintaining strict equipment quarantine practices.
References
Mid-Atlantic Apiculture Research and Extension Consortium. Beekeeping Basics (Penn State University).
URL: https://portal.ct.gov/-/media/caes/documents/bee/penn_state_beekeeping_basics_agrs93.pdf
Exact Section: Found in the 'Diseases of Adult Honey Bees' section (pages 83–84), which explains the life cycle of Nosema Apis and describes the gathering of bee samples for diagnostic analysis.
Plant Health Australia. Biosecurity Manual for Beekeepers.
URL: https://www.planthealthaustralia.com.au
Exact Section: Found in the 'Adult Bee Diseases' reference sheets (pages 16–18), outlining the physical indicators of viral infections and the role of Varroa destructor as a primary vector.
North Carolina State University Cooperative Extension. Disease Management and Guidelines for the Honey Bee.
URL: https://content.ces.ncsu.edu/disease-management-and-guidelines-for-the-honey-bee
Exact Section: Found in the 'Adult Parasites and Pathogens' table and management recommendations, with a focus on distinguishing dysentery from systemic Nosema infections and specifying appropriate sanitation steps.