Uptake of Neonicotinoid Insecticides by Water-Foraging Honey Bees (Hymenoptera: Apidae) Through Guttation Fluid of Winter Oilseed Rape

The water-foraging activity of honey bees (Apis mellifera L.) on guttation fluid of seed-coated crops, such as winter oilseed rape (WOR; Brassica napus L.), has not yet been evaluated. We analyzed the uptake of active substances (a.s.) in guttation fluid by evaluating residues of honey-sac contents....

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Bibliographic Details
Published in:	Journal of economic entomology Vol. 109; no. 1; pp. 31 - 40
Main Authors:	Reetz, J. E, Schulz, W, Seitz, W, Spiteller, M, Zühlke, S, Armbruster, W, Wallner, K
Format:	Journal Article
Language:	English
Published:	England Entomological Society of America 01-02-2016 Oxford University Press
Subjects:	Animals APICULTURE AND SOCIAL INSECTS Apis mellifera Autumn Bees Bees - physiology Brassica napus - metabolism Chromatography, High Pressure Liquid Chronic exposure Coatings Dormancy Feeding Behavior Flowering Foraging behavior Germany Guanidines - metabolism guttation Honey honey sac Imidazoles - metabolism Insecticides Insecticides - metabolism Mass Spectrometry Nectar neonicotinoid Neonicotinoids Nitro Compounds - metabolism Oxazines - metabolism Pesticide Residues - analysis Plant Leaves - metabolism Plant Nectar - chemistry Plants (botany) Pollen Pollen - chemistry Rape plants Residues Seasons seed coating Seed coats Seeds Thiamethoxam Thiazoles - metabolism Water - metabolism Water demand Winter winter oilseed rape neonicotinoid guttation seed coating winter oilseed rape honey sac
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Summary:	The water-foraging activity of honey bees (Apis mellifera L.) on guttation fluid of seed-coated crops, such as winter oilseed rape (WOR; Brassica napus L.), has not yet been evaluated. We analyzed the uptake of active substances (a.s.) in guttation fluid by evaluating residues of honey-sac contents. In autumn, insecticide residues of up to 130 µg a.s. per liter were released in WOR guttation fluid; this concentration is noticeably lower than levels reported in guttation fluid of seed-coated maize. Until winter dormancy, the concentrations declined to <30 µg a.s. per liter. In spring, residues were linked to prewintered plants and declined steadily until flowering. The maximum release of residues in guttation fluid of seed-coated WOR occurs on the first leaves in autumn when the colonieś water demand decreases. For the first time, proof for the uptake of guttation fluid from seed-coated WOR by honey bees was provided by measuring residues in individual honey-sac contents. In total, 38 out of 204 samples (19%) showed residues of thiamethoxam at concentrations ranging from 0.3 to 0.95 µg per liter while the corresponding concentrations in guttation fluid of WOR varied between 3.6 to 12.9 µg thiamethoxam per liter. The amounts of thiamethoxam we found in the honey sacs of water-foraging honey bees were therefore below the thresholds in nectar and pollen that are considered to have negative effects on honey bees after chronic exposure.
ISSN:	0022-0493 1938-291X
DOI:	10.1093/jee/tov287