Tuesday, May 5, 2015

Honey Bee Health and the Critical Link to U.S. Agriculture

Most of us are aware of the role honey bees play in the pollination of plants in the United States but what many don’t realize is how critical they are to commercial crop production. While there are several native pollinators in the U.S., the honey bee was introduced to the New World when European settlers arrived. The honey bee proved to be much more prolific and colonies easy to manage as agriculture expanded across the nation. Honey bees have become indispensible for the production of several crops as evident by the complete dependence of the California almond industry on some 1.4 million colonies, representing ~60% of all colonies in the U.S managed for crop production. Commercial production of several other crops including nuts, fruits, berries and vegetables also depend on pollination by honey bees.
Unfortunately, the U.S. has seen a significant decrease in the total number of managed colonies from ~5 million in the 1940s to 2.5 million today! Along the way the loss and replacement of approximately 10 million bee hives came at a replacement cost of ~ $2 billion. The trend has also been seen on a global scale coinciding with an increased demand for pollination services for commercial operations.

While the disappearance of colonies is well documented, the problem remains a mystery designated Colony Collapse Disorder (CCD). Symptoms of the syndrome include the absence of adult bees or dead bee bodies in the presence of a live queen and brood as well as honey in the hive. The decline in the U.S. has been associated with the introduction of several new pathogens and pests in the 1980s and carriers of viral agents such as Varroa and tracheal mites during the 1990s. However, no single scientific cause has been verified to date leading to CCD. Research suggests rather, that a combination of environmental and pathological stresses can lead to CCD.

Current research has defined the four general categories mentioned above as probable causes contributing to CCD: 1) Pathogens, 2) Parasites, 3) Management stressors and 4) Environmental stressors. Field surveys and laboratory research have supported a number of potential causes yet none have held up to rigorous examination leading to a definitive “cause” of CCD.

One such area of research investigates the affect of the gradual speciation shift in favor of the microsporidia pathogen Nosema ceranae over N. apis via a survey of bee hives across the U.S. Data suggest that infection immunosuppresses honey bees and negatively affects nutrient utilization negatively impacting colony health. Pathogen load via a spore count can be indicative of the health of the colony and generally requires sampling several bees from numerous hives; typically ~ 8-10,000 samples are surveyed over the typical active bee season. Currently the survey relies on manual counting methods similar to blood cell counting using a hemocytometer. BioTek has been working with researchers to provide an automated solution to handle examination of the complex samples of macerated bees. The use of the Cytation 5 at higher magnification (20x) in conjunction with a disposable hemocytometer offers a possible automated solution for determination of spore count (figure 1). Keep tuned for further developments as we continue to work towards validation of this methodology.

Image taken at 20x magnification.
Figure 1. Image taken at 20x magnification. Macerated bee sample visualized using phase contrast at 20x magnification. Spores outlined in yellow fit the criteria for intensity, size and circularity while those outlined in red are excluded by non-conformity to the defined circularity criteria

By: BioTek Instruments, Peter J. Brescia Jr., MSc, MBA

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