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.

Standard methods for toxicology research inApis mellifera

“…It has been shown that bees can be contaminated with potentially lethal doses of insecticide simply by flying in the vicinity of a pneumatic drilling machine using seeds coated with insecticide (Marzaro et al, 2011;Girolami et al, 2012). The fragments of this coating are emitted into the atmosphere and constitute a toxic cloud the size of which may be estimated at some tens of metres in diameter.…”

“…Observations are done at the level of the colony and only individual observations on bees are included insofar as they may affect colony development. In principle, guttation water would not be a major source of exposure given that normally these droplets occur mainly in early plant developmental stages (Girolami et al, 2009;Tapparo et al, 2012). However, the individual geographical and meteorological conditions of each area should be considered to exclude this potential exposure route.…”

Interaction between pesticides and other factors in effects on bees

“…Using this theoretical air concentration an exposure level for bees flying to and from their foraging areas can be calculated by multiplying the air exposure volume by the insecticide air concentration, resulting in a dose of 9.2 ng/bee, a deposition rate of 6.25 ng/bee per 1μg ai/ m 3 . The far higher levels reported when bees were held in cages (Tapparo et al, 2012) reflects an artificial situation in which bees could not move through or away from the dust plume. This is demonstrated by the lower residues in live bees sampled at the hives following application of clothiandin treated seed in which residues of 1.8 ng/bee were detected (Chauzat, Martel et al 2010) which suggests that the use of the concentration in air over the treated field may be protective but not unrealistic.…”

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 1: new molecules, metabolism, fate, and transport

“…Pneumatic planters are widely used and have been identified as a source of dispersion of abraded particles during maize drilling since 2003 (Greatti et al 2003). Many other field experiments identified sowing with pneumatic drilling machines as an important source of environmental contamination (Krupke et al 2012;Pochi et al 2012;Tapparo et al 2012). The release into the atmosphere of particulate matter containing insecticides causes the contamination of vegetation surrounding the field, with the consequent exposure of nontarget animals to sublethal dose of insecticides (Greatti et al 2006;Stewart et al 2014).…”