Inside PBS Blog

An episode of NATURE called “Silence of the Bees” has kept viewers buzzing about honeybees since it first aired. To learn more, we sent Dr. Diana Cox-Foster, a biochemistry researcher at Penn State University, your questions about the mysterious and sudden decline of honeybees. Dr. Cox-Foster has researched the strange phenomenon striking the country’s hives and here are her responses.

Is there any evidence that genetically modified plants are to blame for the bee decline? Audrey

This is one of the most common questions that people ask. Genetically modified organism (GMO) crops were among the first potential causes that researchers in the United States considered when CCD was reported in honey bees. Even before the initial reports of CCD, experiments were done by a research team from the University of Maryland and the USDA to ask if crops genetically engineered to express the insecticidal-protein toxin from the bacterium Bacillus thuringiensis (Bt) would be harmful to honey bees. Previously, researchers had examined the specificity of the Bt toxins and found that there were primarily three groups of insects affected by different Bt toxins: butterflies/moths, mosquitoes, and beetles. In experiments testing the commonly used Bt’s, honey bees are not affected, primarily because conditions in their digestive tracts differ from these other insect groups. In the multiple experiments performed by the researchers from Maryland and USDA, they feed bees on pollen from plants that had been genetically engineered versus the same plant lines (isolines) that lacked the toxin. No negative effects by the GMO pollen were observed. The researchers also thoroughly looked at all studies worldwide that have examined non-target effects on honey bees by GMO crops that expressed insecticidal toxins. Again, there is no evidence to support GMO crops as a factor underlying the declines in honey bees. (See http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001415 and a summary of experimental studies at http://www.maarec.psu.edu/CCDPpt/NontargeteffectsofBt.pdf).

The health of the honey bee immune systems is a major concern to researchers. At the current time, many researchers are asking bee immune systems could be suppressed by chemical exposure to sub-lethal levels of environmental pesticides or if there are new combinations of diseases present that may suppress the bee’s immune defenses. Research is being done to ask if Bt toxins are among those chemicals that could impair bee immune systems in combination with other factors; however, Bt is low on the list of suspects.

Since bees are so important, and it appears that they are in a lot of trouble why is there no push by scientist to put them on the endangered species list? Bill

This is a good question. The honey bee (Apis mellifera) is a non-native species to the United States. The original European colonists brought honey bees with them as they crossed the ocean and established their homes here. Honey bees are truly the world’s domesticated insect livestock and are now found world wide. The native host-range of several species and sub-species of honey bees is found in Europe, Africa, and Asia. At this time, there is no danger of the various species of honey bees themselves going extinct.

With that said, we do have serious concerns about the survival and availability of managed colonies of honey bees. In the United States and other countries, production of many food crops is dependent upon the pollination services provided by honey bees. In the United States, our agricultural systems have changed over the last century and we are now highly dependent upon the movement of honey bees from one major crop to another. Many crops are planted in such a way that native bees are no longer available for pollination. In several regions and countries in Asia, there are reports of a lack of honey bees for pollination of crops. Some farmers in these countries have had to resort to hand pollination, or crop yields are greatly reduced or poor. In the United States, we are concerned about the future sustainability and security of our food that depends upon pollinators.

It is not only the honey bees that are in trouble. In a 2006 report issued by the National Academy of Sciences (read the report here: http://dels.nas.edu/pollinators/) and in reports from many other countries, we know that other species of pollinators (native bees, butterflies, other insects, bats, and hummingbirds) are in grave danger. Several species may have gone extinct or their populations are severely declining (read more at http://www.xerces.org/pollinator-conservation/). Many of these pollinators are closely associated with native plants that depend upon these pollinators for survival. Thus when the pollinator goes extinct, its partner (the native plant) is also endangered and may go extinct.

I have read about ways that people can help the bees. One I've read about is planting things that will attract bees. What sort of bee friendly plants would you recommend. What else could people do to help in this crisis? Michelle

We do think that every individual can make a difference by planting pollinator-friendly flowers to provide food (nectar and pollen) and habitat for the bees and other pollinators. The plantings can be as big as a wildflower meadow or as small as a window box. Even the roofs of houses and buildings can be made bee-friendly, by planting green roofs or living walls with flowering plants that provide nectar and pollen for pollinators. Ideally the plants chosen will be native plants that are adapted for the area and will be naturally more resistant to pests and diseases. A mixture of flowers, shrubs, and trees that bloom over the entire season is the best choice. Information about what types of plants to choose for your particular area can be obtained from your local Master Gardeners (contact your local extension office) or you can download planting guides for your particular habitat. (See these web sites for more info: http://www.pollinator.org/guides.htm or http://dels.nas.edu/pollinators/index.shtml). The gardens should ideally also have clean water sources and provide habitat for the various types of bees and other pollinators.

To help in other ways, individuals can also minimize their use of pesticides, such as insecticides, herbicides, and fungicides. There are indications that these chemicals are more widespread in the environment and that bees may be exposed to levels that affect them and their ability to fight-off diseases. If you do need to use a pesticide, choose one that is bee-friendly (read the label, under warnings or cautions); and read and closely follow the directions on the label. (If the label says to only apply a small amount, then really you only need to apply a small amount. More is NOT better.) If you have questions about the pesticides and how to use them, contact your local extension office or the manufacturer.

Another way to help the bees is to support your local beekeepers. Buying honey or allowing beekeepers to keep hives on or near your property will help the honey bees.

Do you think we need to change our demands on fresh produce and how we care/tend our open green spaces to promote a more friendly environments for the small guys like the bees and frogs that have been disappearing? GBR

We have to thank pollinators for one out of every three bites of food that we eat each day. This is not only includes those fresh fruits that we love to eat, but almost all our vegetables and even forage crops (like alfalfa and clover) that our meat and dairy animals eat. These crops depend upon bees and other pollinators for seed production. Planting gardens and natural areas with flowering plants and supporting local gardeners and farmers that grow their crops in a pollinator-friendly manner will help the bees and other pollinators. As described above, minimizing pesticide use will benefit bees. These actions will not only help the pollinators but will help the other creatures that also depend upon them, like the frogs, the bats, etc. Helping bees is crucial to not only humans and our food supply but also essential for the natural ecosystems around us. The reproduction of plants via pollination is a keystone for life as we know it.

With so many cases of disturbance in our ecological balance concerning the small warning creatures, CCD in honey bees, OE in monarch butterflies, White nose fungus in small brown bats,there has to be an environmental trigger of sorts. What are the chances that these incidents are related and how can we track the problem? Lou-ann

Scientists from many disciplines are trying to determine if these incidents are related by learning what factors underlie each of the declines. At the current time, we have no evidence to suggest that a simple set of factors is shared by all. Additional research is needed not only in the United States, but also in other countries where similar declines are being reported. Large-scale epidemiological studies will enable careful dissection and comparison of the problems. Funding is essential for these studies, ranging from analysis of diseases, chemical exposure, impacts of climate change, etc. It is crucial that these studies be performed now and that the information is widely shared and used as soon as possible to correct or remediate the issues.