Which of the following is a sign of a stress disease in bees?

European Foulbrood is recognized as a sign of stress disease in bees primarily due to its association with environmental factors, poor nutrition, and other stressors that can compromise the health of the hive. This disease is caused by the bacterium Melissococcus plutonius, which often proliferates when bees are weakened or stressed, leading to increased vulnerability to infections.

In healthy colonies, bees are generally able to withstand some level of bacterial infection; however, when bees are under stress—such as from lack of food sources, poor weather conditions, or pest infestations—they become more susceptible to European Foulbrood. Consequently, the presence of this disease often serves as an indicator of underlying problems affecting the colony's overall wellness, reflecting the impacts of stress on bee health and longevity.

While American Foulbrood, Varroa mite infestation, and Nosema can also have detrimental effects on bee populations, they may not directly signify a stress response in the same way that European Foulbrood does. Thus, the connection between European Foulbrood and the stress condition allows for a clearer understanding of colony health issues.