Colony collapse disorder, the mysterious syndrome where honeybees disappear from their hives and never return, has plagued the beekeeping industry for over half a decade, threatening the world's supply of bee-pollinated crops (that's just about every pleasurable food you can think of). It's obvious by now that there is no one single villain in this story. Poor nutrition, varroa mite infestations, fungicides, and certain pesticides all contribute to the problem.
We already know that neonicotinoid plant pesticides, which disturb bees' central nervous system, are used in commercial agriculture around the world. According to a study co-authored by the Pesticide Research Institute and Friends of the Earth, supposedly bee-friendly garden plants found at popular retailers like Home Depot and Lowe's are also harboring these pesticides, which are used in systemic treatments for plants that are attractive to bees.
Researchers looked at flower and vegetable plants (including summer squash and tomato) from Home Depot, Lowe’s, and Orchard Supply Hardware in Minneapolis, Washington, D.C., and the San Francisco Bay Area. Guess what they found?
Neonicotinoid residues were present in 54% of the 13 samples, with concentrations ranging from 11 to 1,500 micrograms per kilogram of plant (that's over 200 times higher in some cases than agricultural crop residues). Some plants tested positive for two or three types of neonicotinoids—meaning they were treated multiple times before making their way onto store shelves. Bees are exposed to the residues when they forage on contaminated plants.
From the report:
All of the samples with detections could potentially cause sublethal effects and mortality in pollinators following chronic exposure. Beyond acute pollinator mortality from bees receiving a lethal dose, neonicotinoids contribute to impairment in immune response, learning and memory, hive communications, and reproduction at doses far below those that cause bee kills...Because the neonicotinoid pesticides are systemic and persistent, exposures to low levels of neonicotinoids in pollen and nectar over an extended period of time (weeks to months) is a serious consideration.
The study's recommendations are obvious: nursery operations should stop using neonicotinoid insecticides and only work with untreated seeds—as should home gardeners, larger institutions, cities, counties and states. Without legislation (another recommendation), this probably won't happen—people are lazy and inertia is a powerful force. The European Union's partial ban on neonicotinoids, however, suggests that some countries are at least making progress on the issue.