CENTRE NATIONAL DE LA RECHERCHE
Règlement CE 1221/97
Convention MAP/ CNRS N° 081.0810.00 et 081.0900.00
1999 and 2000 programs
AFSSA - CNRS - INRA
Rapport de résultats n° 3 au Ministère de l'Agriculture et de la Pêche - June 2000
Dr J.-M. BONMATIN (CNRS) Dr E. R. BENGSCH (CNRS)
Dr I. MOINEAU (CNRS) Dr S. LECOUBLET (CNRS)
Dr M. E. COLIN (INRA) Dr C. FLECHE (AFSSA)
Our HPLC-MS/MS analytical methodology is fully validated. It allows for the detection of IMIDACLOPRIDE (active material in
"Gaucho®", Confidor, Férial) from levels of 0.1ppb and to quantify from levels above 1ppb.
Accordingly, the study of the bioavailability of IMIDACLOPRIDE in plant material is pertinent with regard to doses that provoke sub-lethal effects in bees.
These effects are found to be situated below levels of some ppb or nano-grammes of IMIDACLOPRIDE per bee (NOEC less than 3ppb).
The situation maybe made worse by the presence of metabolites, some of which are equally, if not more toxic than IMIDACLOPRIDE itself (annex 2).
We have studied the bioavailability of IMIDACLOPRIDE in plant material treated with "Gaucho®" and also its persistence in soils that have subsequencialy been planted with crops not treated with "Gaucho®". Sunflowers and Maize treated with "Gaucho®" contained IMIDACLOPRIDE in all parts of their vegetation, particularly flowering parts at levels about 10 ppb. In the field, a phenomenon of increased levels at flowering period was proved, probably allied to increased metabolic activity during the production of seed.
Whenever crops were treated with "Gaucho®", soils contained imidaclopride at levels of several tens sometimes hundreds ppb. A year later, the IMIDACLOPRIDE persists at on average a level of 5 ppb. Two years later, the toxin is still present and it appears that three years are necessary for it to be no longer detectable (less than 0.1ppb). This field data illustrates the high persistent characteristic of IMIDACLOPRIDE in soils, knowing that its high duration period is disputed by others (DT50 in the order of 6 to 9 months). Wherever there are successive treatments of "Gaucho®", it has not been possible to exclude that residual levels generate an accumulation in soils, this especially so due to the possibility of soils being able to receive two crops treated with "Gaucho®" in the same year. Non-treated crops are capable of absorbing the residual IMIDACLOPRIDE from soils previously contaminated by one or several treatments of "Gaucho®". The transfer from soil to plant of IMIDACLOPRIDE is particularly effective in the cases of Sunflower and Maize, which present a major interest for bees. This transfer is as well effective in the flowers of unsown plants (volunteer plants) which are frequently visited by bees.
These studies permitted the validation of the protocol put in place for the collection of sample material from the field, established by the pilot committee in 1998, since no accidental contamination was observed. Even more it explains probably why in 1998 the symptoms of chronic intoxication in bees were observed on control sites as well as in the "Gaucho®" treated sites. Also, why significant differences between the two types of site did not show in results from other measurements taken. Effectively, Sunflowers in control areas were not totally free from IMIDACLOPRIDE.As well; the control areas were treated with one or more other insecticides (lindane,carbofurane, fipronil…) able also to be toxic for bees. Due to this fact, it clearly appears that the field comparisons should be done against those crops grown on "organic" parcels of land.
If the (very) long term effectiveness of the insecticide "Gaucho®" in no longer in doubt, its environmental compatibility at the approved dose is necessarily disputable. In effect, it appears that there is no factor of security (generally that of 10 times or more) between the doses of IMIDACLOPRIDE provoking sub-lethal effects and its bioavailability in field conditions.