The Pesticide Research Institute found that seven of 13 types of garden plants purchased at top retailers contained neurotoxic pesticides that could harm or kill bees and other pollinators.
Researchers looked for the presence of such pesticides, known as neonicotinoids, in plants at garden centers in Washington, D.C., the San Francisco Bay Area and Minneapolis. The study was co-authored by the Pesticide Research Institute and the environmental organization Friends of the Earth.
Susan Kegley, a California beekeeper who is the CEO of Pesticide Research Institute, feared that people who think they're buying pollinator-friendly plants might be doing more harm than good.
"Bees are in trouble already," she said. "What we'd like, as home gardeners, is to have the gardens to be a place of refuge for the bees, and not another area that's poison for them."
COMPLEX MIX OF PROBLEMS
The pesticides remain in the plants and soil and can continue to affect pollinators for months, or even years, after the treatment, Kegley said.
Retailers either should insist that their suppliers stop using neonicotinoid pesticides or should label them so consumers can understand the danger their purchase could pose to bees.
Companies that make pesticides have fought back about claims that neonicotinoids are the cause of widespread bee die-offs. They've been particularly vocal about the European Union's move toward banning products that contain neonicotinoids.
When the EU announced the ban last spring, Bayer CropScience said the action distracted attention from issues that the company thought were responsible for the threats to bee populations. More likely causes, the company said, include mite infestations, diseases and viruses, and the need for more nectar-rich habitats.
The company, one of the largest manufacturers of such pesticides, didn't respond to a request for comment before the study was released. It's said previously that banning such pesticides will put at risk farmers' ability to destroy pests that can severely damage crops.
But many scientists and beekeepers are worried that there hasn't been enough research into the cumulative effect of pesticides.
A report last spring by the Environmental Protection Agency and the U.S. Department of Agriculture suggested a complex mix of problems. It blamed parasites and disease, genetics, poor nutrition and pesticide exposure, as well as farming practices that fail to give bees a pesticide-free buffer zone to forage in heavily developed agricultural regions.
Earlier this month, the University of Maryland released a study building on government research that found bees are more susceptible to a lethal parasite when they're exposed to fungus-killing chemicals. Researchers don't yet know why. They were surprised by the levels of fungicide in hives, and they said the chemical had a measurable effect on bees' ability to fight infection.
They're calling for federal regulations to restrict the use of fungicides, which had been seen as safe for bees, at times when pollinating insects are foraging. The regulations would be similar to those for insecticides.
Bee colony collapse first emerged in 2006. It now touches all aspects of North American agriculture. The USDA estimates that a third of all food and beverages are made possible by pollination, mainly by honeybees. Pollination contributes to an estimated $20 billion to $30 billion in U.S. agricultural production each year.