The decline of honeybees due to colony collapse disorder has garnered a lot of attention in the last few years. But populations of native bees like bumblebees are also showing a downward trend. With fewer honeybees around to pollinate plants, the role of these native pollinators becomes even more vital.
Recent research done by Jonathan Larson, a doctoral student at the University of Kentucky, showed that a threat to bumblebees comes from a certain class of systemic pesticides known as neonicotinoids applied to lawns. He found that exposure to the necnecotinoid clothianidin slowed bee foraging, increased the mortality of worker bees, and had a negative effect on queen production.
Systemic pesticides are taken up by the plants they are applied to, and bees are exposed to the chemicals through the pollen and nectar they collect as they visit treated plants in flower, such as those of clover or weeds commonly found mixed in with turf. One way to avoid this problem is, of course, for home gardeners and commercial lawn care professionals to avoid the use of this class of pesticide.
But, suggests Larson, simply mowing the lawn to remove flowers either immediately before or after pesticide application may keep bumblebees from harm. He found that when treated clover flowers were mowed and new flowers allowed to grow to replace them, bumblebee colonies were not adversely affected. Says Larson, ″Direct contamination of the flowers is the problem, so homeowners need to remove the flower heads of weeds either before or after applying an insecticide to prevent exposure to native pollinators.″
Lawns cover millions of acres in this country, so lawn care practices can have a big impact on pollinators and other aspects of the environment. Larson's goal is to come up with ways that people who choose to treat their turf with insecticides can do so without harming our precious native pollinators.
To read more about Larson's research, go to UK Ag News. (Photo courtesy of Bonsak Hammeraas, Bioforsk -- Norwegian Institute for Agricultural and Environmental Research, Bugwood.org)