Environment & Science
8:38 pm
Thu June 26, 2014

Gardeners beware: Study shows harmful pesticide in garden store plants

2 out of 4 plants from a suburban Detroit Home Depot tested positive for neonicotinoids.
Credit Sarah Cwiek / Michigan Radio

A Michigan environmental group says gardeners should be careful when buying plants – they may be inadvertently harming bees.

The Ann Arbor-based Ecology Center was part of a study looking at the pesticide content in plants bought from major home and garden stores in 18 cities across North America.

Of four plants purchased at a metro Detroit Home Depot, two tested positive for neonicotinoids, a class of pesticides known to be toxic to bees.

That reflects the study’s overall findings, with just over 50% of all the plants sampled testing positive for neonicotinoids.

The Ecology Center’s Melissa Cooper Sargent says it’s a “systemic” toxin that gets drawn into a plant’s internal system. So when bees drink in pollen and collect nectar, they’re also taking in pesticides.

“They’re taking a drink of poison, really,” Sargent says. “And then they’re taking it back to the hive and sharing it.”

Sargent says gardeners who are trying to “do the right thing” might actually be making things worse.

“They buy plants that they know the bees will enjoy, (and) provide some habitat for the bees through these plants,” Sargent says. “Yet half of the plants that we’re buying end up poisoning the bees.”

Environmental group are pressing major retailers to stop selling products that contain neonicotinoids, as scientists express growing alarm over declining bee populations worldwide.

Researchers aren’t exactly sure what’s causing bees to disappear, but think it’s likely a complex mix of environmental factors.

And a growing body of research points to neonicotinoids as a major contributing factor.

Detroit beekeeper Joan Mandell says this has been “the worst year for bee decline in Michigan” that anybody can remember.

She says the harsh winter was a big cause, but likely not the only one.

“That alone might’ve killed bees, and did,” says Mandell. “But already, their systems are weakened by things like neonicotinoids.”