Assessment of the Environmental Exposure of Honeybees to Particulate Matter Containing Neonicotinoid Insecticides Coming from Corn Coated Seeds

ABSTRACT: Since seed coating with neonicotinoid insecticides was introduced in the late 1990s, European beekeepers have reported severe colony losses in the period of corn sowing (spring). As a consequence, seed-coating neonicotinoid insecticides that are used worldwide on corn crops have been blamed for honeybee decline. In view of the currently increasing crop production, and also of corn as a renewable energy source, the correct use of these insecticides within sustainable agriculture is a cause of concern. In this paper, a probable - but so far underestimated - route of environmental exposure of honeybees to and intoxication with neonicotinoid insecticides, namely, the atmospheric emission of particulate matter containing the insecticide by drilling machines, has been quantitatively studied. Using optimized analytical procedures, quantitative measurements of both the emitted particulate and the consequent direct contamination of single bees approaching the drilling machine during the foraging activity have been determined. Experimental results show that the environmental release of particles containing neonicotinoids can produce high exposure levels for bees, with lethal effects compatible with colony losses phenomena observed by beekeepers.

Some of the findings:

"In conclusion, particulate matter released by the drilling machine during the sowing of corn seeds coated with neonicotinoid insecticides represents a significant mechanism of environmental diffusion of these insecticides. Bees flying over the sowing field and approaching the emission cloud of the drilling machine can efficiently intercept the suspended particles being directly contaminated with elevated dose of insecticide, significantly higher than the LD50 values estimated for contact, with the cuticle, administration."

"the modifications of the air outlet of drilling machines so far adopted seem to have a limited effect on both the factor emission and the effective bee contamination."

"This emission source of particles with acute toxic effects on bees (and on other insects too) is of concern for both apiculture and crop productions based on bee pollination. But it is also a widespread ecological problem that, in view of the worldwide increase in corn production partly promoted by government subsidies to renewable energy sources, and the consequent predictable exacerbation of the problem, should require a deeper analysis of the related agricultural policies. In this connection, immediate contributions for the reduction of atmospheric factor emissions of neonicotinoid insecticides should come from studies oriented to the realization of suitable devices for an efficient reduction of toxic particles inside the seed distribution mechanism of drilling machines and supported by quantitative data both on particulate emissions and biological effects on honeybees."

Andrea Tapparo, Daniele Marton, Chiara Giorio, Alessandro Zanella, Lidia Solda, Matteo Marzaro, Linda Vivan, and Vincenzo Girolami (in press). Assessment of the Environmental Exposure of Honeybees to Particulate Matter Containing Neonicotinoid Insecticides Coming from Corn Coated Seeds, Environmental Science and Technology

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