The large slice of American agriculture that relies on honeybee pollination is in danger. But colony collapse disorder—the phenomenon where bees mysteriously disappear from their hives—isn’t caused by any one thing. Parasites, viruses, climate change, and pesticides have all contributed to the precipitous decline in the honeybee population over the past half decade. Some of these factors we can’t control, but it is certainly possible to limit pesticides. A new study (PDF) from Purdue explains how toxic insecticides that are used to coat soybean and corn seeds are ending up in bees.
Neonicotinoid insecticides, which have been in use since the mid-1990s, disrupt the central nervous system of pest insects by releasing insecticides into plants. It’s effective enough, but the EPA knows that neonicotinoids are dangerous to bees. The agency has even suggested (PDF) adding this warning label to clothianidin (a kind of neonicotinoid): "This compound is toxic to honey bees. The persistence of residues and the expression clothianidin in nectar and pollen suggest the possibility of chronic toxic risk to honey bee larvae and the eventual stability of the hive."
The research from Purdue—based on analysis of bees and hives in Indiana over a two year period—suggests that nectar and pollen isn’t the only vector for neonicotinoid transmission to bees. The insecticides are found in waste talc released by farm machinery during corn seed planting, in nearby soil (even in unplanted fields), as well as on dandelion plants near the fields, which are visited by bees. The researchers also discovered that corn pollen from treated seeds, which is collected by honeybees, contained the toxic pesticides. Neonicotinoids were found in all samples of nearby dead bees. Even at sublethal levels, the pesticides can affect orientation, brood rearing, and communication.
Neonicotinoids are unlikely to be banned in the U.S. anytime soon (though Germany and Italy suspended their use in 2008), but there are ways to at least manage exposure. The researchers explain: "Our results suggest that of the factors we quantified in this study, used talc exhausted during and after planting (the latter would occur during routine cleaning of planting equipment) stands out as potential routes for exposure that should be prioritized for further quantification and remediation."
In Europe, advanced planting equipment reduces dust generation by 99% compared to the equipment used in the U.S, where there are no guidelines for waste talc disposal or methods to filter exhaust material.
Switching out planting equipment is not even close to a solution to the bee problem (if there is a solution at all). But it’s a small step—and one that our large, bumbling agricultural system could really use.