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We need bees. Of the 100 crops that provide 90 percent of the world's food, 71 are pollinated by bees. Honeybees in particular have been estimated to contribute more than $200 billion to the global economy.

Which is a major reason why there has been such widespread concern over what is now more than a decade of mass die-offs of bees – a phenomenon known as Colony Collapse Disorder (CCD) – in western Europe and the United States. CCD has killed off more than 10 million beehives since 2007 in the U.S. alone, and its contributory causes appear to be complex. One common factor that appears to be prominent, however, is the growth of a new class of pesticides called neonicotinoids. Introduced in the mid-1990s, neonicotinoids are now the fastest-growing class of synthetic pesticides, and have been implicated, not only in killing bees outright by attacking their nervous systems, but also in disrupting their foraging abilities, navigation, learning, communication and memory, and in suppressing their immune systems, making them more vulnerable to disease and pests.

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The toxic potential of these pesticides was underlined when the cosmetic spraying of some linden trees led to the death of 50,000 bumblebees in a Target store parking lot in Oregon. Their toxicity, and particularly the risk they pose to bees, has led to the European Commission imposing a two-year ban on their use on flowering plants, effective this December. Such scientific concerns, and a public campaign by Friends of the Earth, have prompted a number of home improvement stores in the United Kingdom to no longer sell products containing pesticides linked to declining bee populations.

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Partly because the sight and sound of bees is key to the aesthetic of any garden, and partly to combat the impacts of CCS, many home gardeners and beekeepers plant "bee-friendly" gardens, with flowering species that provide habitat and forage for bees and other pollinators. However, according to findings released by Friends of the Earth today, some of those nominally bee-friendly plants may in fact be contributing to the very problem their planters aim to redress.

In a pilot study conducted on FoE's behalf, scientists from the Pesticide Research Institute examined flowering plants such as Salvia and Gaillardia, as well as pollinator-friendly fruits and vegetables such as tomato and squash, purchased from home improvement stores in the San Francisco Bay, Minneapolis/St. Paul, and Washington DC metropolitan areas. They found that of 13 composite samples (from 45 individual plants), seven tested positive for at least one neonicotinoid, with two testing positive for two residues, and a Gaillardia plant from Minnesota showing measurable levels of three different neonicotinoids.

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The reason for this, say the authors of the report, is that long before they reach stores, nursery plants are typically treated with systemic insecticides, which are absorbed through the roots or leaves of the plant and transported to various plant tissues. Although the sample size of this pilot study was relatively small, the authors argue that the high percentage of samples testing positive for neonicotinoids should prompt a wider study.

In the meantime, Friends of the Earth is urging the passage of  the Save America's Pollinators Act, introduced by Representatives John Conyers (D, Mich.) and Earl Blumenauer (D, Ore.), which would suspend seed treatment, soil application, or foliar uses of certain neonicotinoid pesticides on bee-attractive plants until all of the scientific evidence is reviewed by US Environmental Protection Agency, and field studies can be done to evaluate both short- and long-term effects of these pesticides on pollinators.

It is also encouraging gardeners to eschew potentially-treated plants in favor of organic plant starts or growing plants from untreated seeds in organic potting soil. The report's release marks the launch of a new BeeAction campaign, with a website that includes other suggestions – for consumers, retailers, Congress and industry – to take steps on behalf of these most essential of garden visitors.

Photograph by Jean-Luc2005 via Wikimedia Commons