Toxicity tests. Results of a comprehensive field research programme with the systemic insecticide imidacloprid (Gaucho) | [Essais de toxicité. Résultats d'un programme de recherche en champ, très complet, avec l'insecticide systémique imidaclopride (Gaucho)]
2001
Cure, G. ((Bayer France, Puteaux (France). Division Agro)) | Schmidt, H.W. | Schmuck, R.
Gaucho is a registered trademark for plant protection products which contain the chloronicotinyl insecticide imidacloprid and which are used for seed dressing, e.g. on sunflower seed. Sunflower seed are treated with 0.7 mg a.i./grain which is equivalent to 50 g a.i./ha at a planting density of 70,000 plants /ha. In 3 tunnel and 8 field tests it was examined whether this seed dressing could have an influence on honeybees at the time of flowering. Residue analysis of flowers and honeybees were performed to determine the exposure of these pollinating insects during flowering. The residue levels were then compared with effect concentrations as determined in controlled feeding experiments. In none of the 3 tunnel and 8 field tests did the seeddressing with imidacloprid affect the vitality, the foraging activity or the behaviour of the honeybees. From these results it can be reliably concluded that a seed dressing of sunflower seed with imidacloprid has no biological relevance for honeybees. Pollen and nectar of sunflower plants were analysed for the presence of imidacloprid and its relevant metabolites. No quantifiable residue levels were found at a limit of quantitation of 10 ppb. In the controlled feeding experiments under field conditions, no adverse effects were observed on bees fed with spiked sugar solution up to 20 ppb imidacloprid. At higher concentrations (50-100 ppb) honeybees only reduced transitorily the foraging activity which indicates that honeybees realise the presence of imidacloprid at these levels. When these results are compared with the residue levels found in the relevant parts of the sunflower plants it is evident that the findings of the tunnel and field tests are fully confirmed and that no adverse effects on honeybees must be expected from the use of Gaucho in sunflowers
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