Plants used for bee habitat might kill bees

University of Minnesota researchers are studying the effect of insecticide on bees. (Photo courtesy Scott Leddy)

Back yard gardeners who plant bee-friendly plants and flowers, may actually be killing bees. A new report released today by Friends of the Earth, showed that plants purchased at large retailers can contain insecticides toxic to bees and other insects.

Friends of the Earth tested a small sample of 13 plants and seven of the samples  contained neonicotinoid insecticides. While the finding is not a definitive study, it points out that neonicotinoids are found in garden plants purchased at big box retailers. The purchases were made at retailers in San Francisco, Washington D.C. and the Twin Cities.

Researchers say neonicotinoids are now the most widely used insecticides on the market. They are a class of insecticides chemically related to nicotine. They came on the market in the 1990s as a new class of insecticides effective against insects, but much less toxic to humans than other kinds of insecticide.

Neonicotinoids are neuro-active, meaning they work by blocking connections in the insect's brain. They are also systemic in plants; rather than being sprayed on the surface of a plant, they are applied to seeds or soil and the chemicals are then absorbed by the plants as they grow. So the insecticide is in the leaves,  flowers and pollen.  If a bug takes a bite of a plant, it gets a dose of insecticide.

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Because bees have one of the largest brains in the insect world, they have more neuro-transmitters and are more susceptible to this particular kind of insecticide. Bees fly around gathering pollen to bring back to the hive and research is finding that even very low doses of neonicotinoids disrupt their ability to remember where the hive is, or how to find a food source.

I contacted two retailers whose plants were included in the research, Lowe's and Home Depot. Lowe's didn't immediately respond.

Home Depot spokesman Stephen Holmes sent this response:  "We haven’t reviewed the study yet, but we certainly appreciate the importance of the bee population and will be reaching out to the study groups to learn more about their findings and methodology."

The other retailer mentioned in the research is Orchard Supply Hardware, which does not have outlets in Minnesota.

Concern about neonicotinoid insecticides is not new.   Beekeepers believe the insecticide is a factor in a larger problem known as colony collapse, where millions of honey bees die in hives, as I reported earlier this year.  In Europe some of the neonicotinoid insecticides are banned for two years because of the impact on bees.

The insecticide is also widely used in urban landscapes, and at a much higher rate than farmers are allowed to use.  University of Minnesota researcher Vera Krischik, has been studying the effect of neonicotinoid insecticides on bees.  Her findings show that a flower in a backyard could legally contain 200 times more insecticide than soybeans in a farm field. She found those flowers killed bees - sometimes right on the spot.

The U.S. Environmental Protection Agency is doing a standard registration review of neonicotinoids, but that won’t happen for several years. Earlier this year beekeepers, including one from Minnesota, sued the EPA to force an expedited review and restrictions on the use of neonicotinoids. There's also legislation called Save America's Pollinators Act that's been introduced in Congress.

The Friends of the Earth group says this report isn’t definitive science, but is intended to educate consumers. They want gardeners to be aware that the plants they buy might already contain an insecticide. They suggest people grow their own plants from seed, or ask retailers for plants that are not treated with neonicotinoid insecticides.