Study Finds Fungicides May Also Contribute to Declining Bee Populations
The link between popular pesticides and declining bee populations has been the subject of controversy and the target of research for some time; but the soaring use of fungicides hasn’t received much attention as they were accepted to be harmless to the pollinators—until now. Two recent studies found fungicides to be the potential cause for deteriorating health in bumblebee and wild bee populations.
Researchers in one study focused on bumblebees and revealed some startling evidence: bumblebees who visited fungicide-laden blossoms had smaller workers, feeble queens, and overall reduced colony size. In the second study, areas predominantly devoted to agriculture saw an overall reduction in wild bee populations, partly due to widespread fungicide use. Though neither study revealed incontrovertible proof, both found enough correlation between the popular chemicals and worsening bee health to warrant concern.
University of Wisconsin entomologist Hannah Gaines-Day and her team of researchers were asked by local farmers if fungicides were safe to use while crops were in bloom and bees were actively foraging. “It’s a group of pesticides that hasn’t been looked at too closely. Insecticides are meant to kill insects, so people have been really interested in how insecticides kill beneficial insects. But fungicides are not meant to kill insects, so they’ve been passed over,” she explained. Though spraying insect-killing pesticides may be intuitively harmful to bees, the application of fungicides to blossom-heavy crops is common practice.
Previous studies had found fungicides to be safe but had been limited to honeybees; and, even then, only investigated more drastic effects—such as dropping dead within days. Other important species of wild bees and bumblebees as well as critical, lasting effects—like the impact of fungicides on behavior, immunity, and reproduction on long-term health—had not been examined until now.
Gaines-Day and her team of researchers studied five bumblebee colonies confined to areas where the insects’ only option was to forage in plants treated with the standard fungicide dose, so she advised the resulting decrease in colony size and health wouldn’t necessarily translate to normal colonies.
According to the Xerces Society for Invertebrate Conservation, declines in bumblebee populations were observed beginning in the late 1990s. Bumblebees are important pollinators of wild flowering plants and crops and aren’t reliant on a single plant variety for food. They can pollinate in lower light levels and cooler temperatures than other bee species and are uniquely capable of “buzz pollination” which some plants—like cranberries, tomatoes, peppers, and others—are dependent on. Conservation efforts are underway and they invite citizen-observers to participate in the Bumble Bee Watch program.
In the second study, published by the Royal Society, pollinator ecologist Mia Park of the University of North Dakota and her colleagues found “wild bee community abundance and species richness” declined in relation to increasing pesticide use in agriculture-intensive areas, but increased proportions of biodiversity in the landscape had a buffering effect. The same pesticidal qualities of fungicides found in the bumblebee study were also observed, suggesting “deleterious properties of a class of pesticides that was, until recently, considered benign to bees.” Communities of wild bees, according to the study’s abstract,
provide underappreciated but critical agricultural pollination services. Given predicted global shortages in pollination services, managing agroecosystems to support thriving wild bee communities is, therefore, central to ensuring sustainable food production.
Despite the limitations of these studies, the importance of their combined results cannot be overstated. Before fungicide use skyrocketed, the global market for the chemicals in 2005 was estimated at $8 billion, but is projected to account for $21 billion by 2017. Fungicides were commonly used on about 30% of corn, soybean, and wheat crops, according to 2009 estimates. They are thought to be applied to 10%-15% of all crops in the United States.
These figures amount to educated guesswork as there are no current mandatory requirements for reporting fungicide use—a stunning reality check given the utter lack of study on their impacts on pollinators, the environment . . . and humans.