Brood Pattern and Queen Quality
What can Brood Pattern tell us about Queen Quality?
Lee, Kathleen V., Michael Goblirsch, Erin McDermott, David R. Tarpy, and Marla Spivak. 2019. Is the Brood Pattern within a Honey Bee Colony a Reliable Indicator of Queen Quality? Insects 10 (1). https://doi.org/10.3390/insects10010012.
A research team from the University of Minnesota explored the relationship between brood pattern and queen quality. They found that brood pattern was not related to queen size or sperm quantity/viability, but was related to pesticide levels and brood diseases. Find the full article here.
Why did they conduct this research?
Many beekeepers and queen breeders use brood pattern as a tool for choosing high-quality queens. A brood pattern is considered “good” if it contains larvae/pupae of similar age, with few (<20%) open cells; a pattern is considered “poor” if it contains larvae/pupae of different ages interspersed with open cells. You can see examples below (good pattern on the left [or top], poor pattern on the right [or bottom], photo credit: Rob Snyder 2013).
A poor brood pattern can occur when the queen does not lay enough eggs OR when those eggs to not survive until emergence. It can be caused by queen-related factors (not enough sperm, inviable sperm, inbreeding) as well as environmental conditions (brood diseases, pesticide exposure, poor nutrition). The University of Minnesota researchers asked: is brood pattern a reliable way to determine queen quality? What colony factors are associated with good/poor brood patterns?
What did they do?
The researchers selected commercial hives with good and poor brood patterns, and measured health parameters (bee population, queen cell presence, pesticides, brood diseases, Nosema, Varroa, viruses and other pests) over two years. They also measured queen body size and sperm quantity/viability. In the second year of the study, they swapped queens between good-brood and poor-brood colonies and monitored changes to colony health.
What did they find?
The researchers found no differences in queen size or sperm quantity/viability between good-brood and poor-brood hives. They also found no difference in Nosema, Varroa or virus levels. However, when choosing colonies, the researchers found it hard to select poor-brood colonies that did not have clinical signs of brood disease. They also found that the number of pesticide residues was higher in poor-brood colonies. When they conducted the queen “transplant”, they found that the brood pattern of poor-brood queens improved significantly when they were transferred into good-brood colonies, suggesting that environmental conditions might be affecting brood pattern.
The take away?
It’s complicated. This study suggests that a poor brood pattern might be more related to environmental factors (like brood diseases and pesticides) than queen failure. However, certain genetic lines may also be more or less susceptible to brood diseases – in which case queen quality might be judged by brood pattern. The researchers propose other factors (irregular egg-laying, supersedure, low brood production, etc.) that may be more reliable than brood-pattern for diagnosing queen failure. In short, more research is needed to understand the complex interactions between genetics and environment.