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United States Department of Agriculture

Agricultural Research Service

Rapini Project

 

In a Conference on Honey Bee Health held in October of 2012, the research area of greatest importance in the Nutrition section was the availability of forage for honey bees. Before colonies are placed in orchards for almond pollination, they often are kept in holding yards and fed protein and carbohydrate supplements because flowering plants are unavailable. Under these conditions, colony populations can decline so that they no longer are of suitable strength for pollination. In other instances, the colonies die from malnutrition or starvation.

Pollen forager inspecting a rapini flower

Supplemental protein diets can sustain colonies for a short while. However, the benefits on colony health ultimately diminish because the diets do not supply all the nutrients bees need to rear brood or optimize adult bee longevity. If the colonies could have some blooming plants available, nutritional stress might be alleviated and colonies would have a better chance of surviving and building until almond bloom. A plant that blooms in the winter in the southwest and southern California and might supply forage is rapini (Brassica rapa).  We planted a test plot of rapini in the fall of 2012 and found it to be highly attractive to bees throughout the winter.

Pollen forager collecting pollen

Growing plants rather than feeding pollen supplements in the winter is a departure from current beekeeping practices. Data is needed to demonstrate if there is indeed justification for spending resources on plantings rather than on purchasing feed. In 2013, we will collect data comparing protein titers in nurse bees, immune response, and population growth between colonies fed a protein supplement and those foraging on rapini. The study will provide information on whether there are indeed benefits of planting rapini over protein supplement diets in terms of the growth and health of colonies managed for almond pollination. If there is value to beekeepers and almond growers in planting rapini, it will be in colony survival and population growth. Larger colonies have larger foraging populations that can generate greater nut yields.

The project is being funded by the Almond Board of California


Last Modified: 11/4/2013