http://www.digitaljournal.com/news/environment/problems-for-the-usa-population-of-honeybees/article/464011

Long-term study of honeybees reveals troubling trends

Posted Apr 27, 2016 by Tim Sandle
U.S. researchers have completed a five year study of honeybees and parasitic infections. The results are alarming for the future health of bee populations.
Experts explain why everyone should worry about honeybee colony collapse that will affect our food s...
Experts explain why everyone should worry about honeybee colony collapse that will affect our food supply, prices and economy.
Sajjad Fazel (CC BY-SA 3.0)
The aim of collecting the data was to establish a baseline from which the future health of honeybee colonies could be assessed. Around the world bee colonies are in decline, and this has agricultural and economic implications. Bees are the primary pollinators of crops. Reasons for bee colony decline range from ecological changes, the indiscriminate use of pesticides and parasitic infections of hives.
The recent study has focused on the varroa mite, which is a major honey bee pest, and nosema, a fungal parasite. The mite is known for carrying a range of viruses. The mites feed on developing bee larvae.
The data suggests incidences of the pest are more widespread than previously thought and the rate of mite cases is growing. In addition to the mite and fungus, incidences of a non-mite spread viral infection called Chronic Bee Paralysis Virus are growing. This virus causes loss of motor control and it can kill individual bees.
Among the bad news, more encouraging data is that other global killers of bees are not widespread in the U.S. These other infectious agents include the parasitic tropilaelaps mite, the Asian honey bee Apis cerana and slow bee paralysis virus.
Data was drawn from bee colonies in 41 U.S. states, gathered between 2009 and 2014. Data revealed annual trends and patterns relating to seasonality (where mite infestation is higher during the winter.) There were also differences between migratory beehives and stationary ones. Beekeepers who moved hives in order to pollinate different crops had hives which experienced lower incidences of the varroa mite. In general, carefully managed colonies proved to be more robust.
It is hoped the information can lead to some improvements in bee management and provide an epidemiological baseline for future bee conservation work.
The survey formed part of the U.S. National Honey Bee Disease Survey. The study was a joint effort between the University of Maryland and the U.S. Department of Agriculture. The research findings are published in the journal Apidologie, with the paper titled “Multiyear survey targeting disease incidence in US honey bees.”