The researchers, who represented Penn State's College of Agricultural Sciences, University of Liege, Gembloux Agricultural University, North Carolina State University and the U.S. Department of Agriculture's Agricultural Research Service (ARS), collected samples of adult bees, wax comb, pollen and brood – developing larvae – from 91 colonies in 13 apiaries in Florida and California and quantified more than 200 variables, including the presence of parasites such as varroa and tracheal mites; infection by bacteria, viruses and fungi; pesticide levels; nutritional factors; and bee physiology. No single factor was found consistently only in those colonies suffering from CCD.
The study's findings, which were published in the online journal PLoS ONE, illustrate the complexity of solving the CCD problem, according to lead author and Penn State entomologist Dennis vanEngelsdorp. "Our results suggest that this condition may be contagious or the result of exposure to a common risk factor that impairs the bees' immune systems, making them more susceptible to pathogens," said vanEngelsdorp, who also is acting state apiarist for the Pennsylvania Department of Agriculture.
VanEngelsdorp noted that higher pathogen loads are likely to have caused CCD symptoms, but what causes the bees to become infected with so many pathogens is still not known. "Although pathogens seem likely to play a critical role in CCD, that role may be secondary, much like AIDS patients die from secondary diseases," he added.
No one of the screened pathogens had a higher prevalence in colonies that had CCD. There also was no significant difference in the prevalence nor in the total load of varroa or tracheal mites and Nosema, a protozoan that causes disease in bees.
But overall, CCD colonies were co-infected with a greater number of pathogens -- viruses, bacteria and microparasites such as Nosema. For instance, 55 percent of CCD colonies were infected with three or more viruses compared to 28 percent of non-CCD colonies.
The researchers also found detectable levels of residues from 50 different pesticides in all of the sampled colonies, but there was no association between increased pesticide levels and CCD.
In fact, the pyrethroid insecticide Esfenvalerate -- used for a wide variety of pests such as moths, flies, beetles and other insects on vegetable, fruit and nut crops -- was more prevalent in the wax in non-CCD colonies, being found in 32 percent of non-CCD colonies compared to 5 percent of the CCD colonies.
Coumaphos, which is used to treat varroa mites in honeybees, also was found in higher levels in non-CCD colonies.
Entomologist Jeff Pettis with the ARS Bee Research Laboratory in Beltsville, Md., said the study suggests that future research should focus on monitoring parasite, pathogen and pesticide loads, as well as potential interactions among pesticide and pathogen loads. "While the study's results don't indicate a specific cause of CCD, the results do help scientists narrow the direction of future CCD research by showing that some possible causes are less likely," said Pettis.
Study co-authors from Penn State are included Chris Mullin, professor of entomology; Maryann Frazier, senior extension associate in entomology; Jim Frazier, professor of entomology; and Diana Cox-Foster, professor of entomology and Robyn Underwood.
Other researchers included Jay D. Evans and Yanping Chen, ARS; Claude Saegerman, University of Liege; Eric Haubruge and Bach Kim Nguyen, Gembloux Agricultural University, Belgium and David R. Tarpy, North Carolina State University.
Chuck Gill | EurekAlert!
Fighting a destructive crop disease with mathematics
21.06.2017 | University of Cambridge
Unusual soybean coloration sheds a light on gene silencing
20.06.2017 | University of Illinois College of Agricultural, Consumer and Environmental Sciences
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology