Selective breeding of honey bees for multiple traits with a priority on nosema disease resistance

View the project final report

• 2012 annual report
• 2013 annual report

Commodities

• Animals: bees

Practices

• Animal Production: livestock breeding
• Farm Business Management: feasibility study
• Pest Management: genetic resistance
• Production Systems: organic agriculture

The main goal of this project was to improve an available mite resistant honey bee stock by selecting daughter colonies on their performance in a localized setting. Performance measures were based on nosema infection levels, varroa infection, and colony strength. In addition ratings based on visual observations of brood disease, deformed wings, brood pattern, temperament, and runny on comb were conducted. For each year of 2 years a new generation of daughter queens was started. Selection measures were combined in a selection index to aid in determining top performers. The top performers were then selected as breeder queens for the next generation.

To determine if progress was being made in selection, pest levels were compared across 2 generations. Colonies were kept without nosema treatments. In the second year, spring nosema levels were significantly lower in the second generation than first generation colonies indicating that selection on low levels of nosema may be genetically reducing nosema levels in the population. However, without a control population, this determination is not conclusive, but is promising. It was attempted to keep colonies without varroa treatments in the first year, but it became obvious too many colonies would be lost without varroa treatments and they were treated in the second year. Therefore, it was not possible to determine if improvements were made in mite resistance or colony survivorship over winter. Fewer colonies died in the second generation during winter, but this is as likely due to mite treatments as genetic improvements in the stock. Before the 2 years of this project, European foulbrood was a problem in the starting population. For the first and second generation daughter colonies of the starting population, this condition was no longer observed. The starting population breeder queens were selected to be free of European foulbrood and no preventative treatments were given. This is another promising indication that genetic improvement may be occurring in the population based on the reduction of incidence of European foulbrood.

Introduction

Losses in managed honey bee colonies have increased and remained high in recent years. It has become a consensus that multiple causes are responsible for colony losses and many of those causes are related to issues with the parasitic varroa mite and a gut parasite called Nosema. Over the last several decades, major advances have occurred in breeding bees to be resistant to varroa mites by selecting for hygienic behavior. Hygienic, mite resistant bees are being propagated and distributed through many bee breeding programs including the USDA-ARS Varroa Sensitive Hygiene (VSH) bees. However, few of these programs have incorporated selection for nosema disease resistance in parallel to mite resistance. In addition, bees produced in these programs may be adapted to their specific location or conditions not shared by all beekeepers.

Nosema disease is caused by two species of microsporidia, Nosema apis and Nosema ceranae. These unicellular organisms reproduce inside adult honey bees negatively affecting the mid-gut epithelium, hypopharyngeal glands, corpora allata (juvenile hormone), as well as oocytes in queens. Nosema infected bees have a shorter lifespan, dysentery, nutrition digestion problems, cannot produce essential hormones correctly, and in many ways cannot function to maintain productive or surviving colonies. The microsporidia produce spores in infected bees and after defecation, these spores are picked up by un-infected bees to continue the disease cycle. Nosema disease is normally controlled by feeding the antibiotic fumagillin dissolved in syrup during spring and fall. Treatment is normally done without prior sampling to determine if Nosema spore levels are high enough to warrant treatment. In the past, there was a single species involved, Nosema apis. Now, a new Nosema species in U.S. honey bees, Nosema ceranae, causes much more problems than previously observed. This may explain why nosema disease resistance has not already been incorporated into many historic, large scale breeding programs.

Spore sampling for Nosema requires microscopic examination of bee samples and could possibly be used as a selection measure. Although there is some expense to microscopic examination, the procedure is relatively basic compared to other microscopic work. Monitoring varroa levels by mite sampling on adult bees is understood to aid in selection for varroa resistance. In addition to selecting for disease resistance, selecting bees by their performance under the same localized conditions they are to be used is long understood as an effective method to breed honey bees as evidenced in Brother Adam’s, “Beekeeping at Buckfast Abbey”.

Nosema disease is an impediment to organic production in honey bees. Formal recommendations by the National Organic Standards Board to the National Organic Program in 2010 point out that antibiotics are not permitted for any type of livestock. It is unlikely the antibiotic fumagillin will ever be included as an allowed organic substance. There are numerous essential oils on the market for control of nosema disease, however none of these have been shown to work. There is some evidence of variation in response to Nosema by colonies and populations. Some colonies clearly are susceptible to Nosema and die from it while others thrive under the same conditions. There are effective organic treatments for varroa infestations, but not for nosema disease. Selecting colonies for resistance to nosema is likely to effectively control this disease as evidenced by recent work at the USDA Baton Rouge bee lab.

• Establish a realistic protocol to measure colony performance that evaluates disease resistance and productivity.
• Establish numeric data visualization techniques to make comparisons on performance measures.
• Document improvement in the population across generations.
• Distribute stock to local beekeepers.
• Conduct outreach through my website and beekeeping conferences.