Many plants and garden products marketed as "bee friendly" contain a substance deadly to bees and linked to colony collapse disorder, according to a new report, which calls for major U.S. retailers to stop carrying the products.

The news comes at a time of heightened awareness to how crucial bees are to the ecosystem and droves of mindful gardeners are keen to plant and use products that are friendly to bees.

The study, a joint effort by scientists from the Pesticide Research Institute (PRI) and the conservation group Friends of the Earth, determined that seven of 13 types of garden plants sold at top retail chains such as Lowe's and Home Depot and Orchard Supply Hardware contained neonicotinoids -- deadly neurotoxic compounds linked to mass honeybee deaths.

Neonicotinoids are known to poison bees directly and indirectly, either killing the insects or compromising their immune systems and impairing their ability to forage and gather pollen.

Residues of neonicotinoids were found in 54 percent of the products sampled in the study, ranging in concentrations from 11 to 1,500 parts per billion. Researchers suggest that because more than half of the products sampled contained neonicotinoids the problem could be more widespread than the study suggests and that home gardens may have grown to be a source of neonicotinoid exposure to bees.

"The pilot study confirms that many of the plants sold in nurseries and garden stores across the U.S. have been pre-treated with systemic neonicotinoid insecticides, making them potentially toxic to pollinators," said PRI scientist Timothy Brown. "Unfortunately, these pesticides don't break down quickly -- they remain in the plants and the soil and can continue to affect pollinators for months to years after the treatment."

The researchers stress the importance that bee colonies live on; the tiny insects are essential to the food system.

"Bees are essential to the production of one out of every three bites of food we eat. In fact, 71 of the 100 crops that provide 90 percent of the world's food-from almonds to tomatoes and strawberries-are pollinated by bees," the researchers write in their report, "Gardeners Beware: Bee-Toxic Pesticides Found in "Bee-Friendly" Plants Sold at Garden Centers Nationwide."

Major garden retailers in Washington D.C., Minneapolis and the San Francisco Bay area were included in the study.

"Our investigation is the first to show that so called 'bee-friendly' garden plants contain pesticides that can poison bees, with no warning to gardeners," said Lisa Archer, director of the Food and Technology Program at Friends of the Earth. "Bees are essential to our food system and they are dying at alarming rates. Neonic pesticides are a key part of the problem we can start to fix right now in our own backyards," she said.