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Com. 32

Biodégradation de l’isoproturon et variabilité spatiale dans une parcelle agricole

El-Sebai, T.^1,2; Lagacherie, B.²; Martin-Laurent, F.²; Coste, C.³ et Soulas, G.^2
1 NRC, Maladies et protection de plante. Le Caire (EGYPTE)

² INRA,Microbiologies des Sols, DIJON

³ Université de Perpignan, centre phytopharmacie, PERPIGNAN.
La biodégradation accélérée d’un herbicide peut conduire à la diminution de sa demi-vie et donc son efficacité. Elle peut dans certains cas expliquer la présence au sein d’une parcelle traitées d’un nombre croissant de mauvaises herbes qui par ailleurs restent sensibles à la molécule utilisée.

L’objectif de cette étude est d’étudier la possibilité de l’implication de la biodégradation accélérée de l’isoproturon dans la diminution de l’efficacité de cet herbicide utilisé en culture céréalière pour lutter contre des monocotylédones (folle avoine, vulpin). Nous avons également cherché à décrire la variabilité spatiale observée dans la biodégradation accélérée.

Notre étude a été effectuée en conditions contrôlées de laboratoire sur des échantillons prélevés dans une parcelle occupée par le blé l’année de prélèvement et traitée tous les ans depuis plus de 10 ans par de l’isoproturon.

Nous avons caractérisé la dégradation de l’ isoproturon par les paramètres de la cinétique de minéralisation du produit marqué au ¹⁴C sur le cycle. Nous avons également apprécié la taille de la biomasse totale, dénombré la biomasse dégradante, caractérisé la structure spécifique de la microflore (RISA) que nous avons mis en relation avec les caractéristiques physico-chimiques du sol (pH, C/N, CEC).

Il apparaît que dans cette parcelle la dégradation de l’ isoproturon est accélérée et que cette accélération varie selon les prélèvements. Nous avons tenté de relier le phénomène aux principales caractéristiques physico-chimiques du sol.

Com. 33
The main characteristics of a chemical control on Agriotes populations
P.F. Chaton ¹, M.H. Liégeois ², R. Mauras ³, L. Perez ³, G. Merle du Bourg ³, J.C. Meyran ¹, M. Tissut ¹ and P. Ravanel ^1
1 UMR LECA, Laboratoire Perturbations Environnementales et Xénobiotiques, Centre de Biologie Alpine, Université Joseph Fourier, BP 53, 38 041 Grenoble cedex 09,

FAX, ([phone] Tél : [phone]

E-mail [e-mail]

² Scotts France SAS 21, chemin de la Sauvegarde, BP 92, 69136 Ecully.

³ Bayer CropScience, 55, avenue René-Cassin, 69 337 Lyon cedex 09

Samples of different populations of Agriotes sp. were taken up from several places from France. These samples were mostly composed of the Agriotes lineatus species.

The laboratory conditions were established for maintaining the larvae alive for several months and their feeding behavior could be studied. The transtegument penetration of lipophilic xenobiotics was shown to be a very low-rate process. The penetration of a lethal amount of a lipophilic insecticide could be therefore mainly obtained through food absorption. Agriotes larvae are developing slowly in the soil, generally for four years before giving the flying imagos. It was demonstrated that soil organic matter was not abundantly consumed but that storage components of plant seed and seedlings were very appetent. This appetancy was maximum for the mixture of starch, lipids and different types of smell molecules.

The alimentary rythm of Agriotes was very complex, depending on climatic conditions and on an endogenous comportment bound to the moulting rythm.

When larvae were unable to find germinating seeds, they could penetrate inside older corn seedling digging a hole at the level of the second node of the stem and eating the meristematic organs. This induced very typical symptoms on the aerial parts of corn, concerning the shape of the leaves and the chlorophyll synthesis. The meristematic disturbance was, in fact followed by a deep change in protein synthesis, which could be simply shown by chlorosis of the leaves. The chemical control of Agriotes populations was obtained with insecticides such as fipronil by associating it with the food, most often through seeds treatments.

Com. 34
Photochemical degradations of imazaquin in aqueous solutions
H. Barkani*^§, C. Emmelin*, M. El Azzouzi^§, J.M. Chovelon*

Laboratoire d'Application de la Chimie à l'Environnement, LACE, UMR 5634 Université Claude Bernard Lyon1

Université Mohamed V, Agdal-Rabat (Maroc)
The imidazolinone family is one of the new classes of low application-rate herbicides (0.10 kg /hect) increasingly used for cultures such as soybean and corn. Their activity comes from the inhibition of AcetoxHydroAcid Synthase (A.H.A.S.).

The photodegradation of imazaquin, a herbicide belonging to the family of imidazolinones, was studied at six different pH values. HPK (pyrex) lamp and Suntest lamp (Xenon arc lamp) were used as radiation source. Photodegradation products were analysed and monitored using HPLC-UV and HPLC-MS.

It has been found that he photodegradation of imazaquin is more important at pH 5,7,9 than at pH 2,3 and 4.

As it is known that the fate and degradation of chemicals is natural water are affected by interactions with humic substances (HS), photochemical degradations have also been studied using three concentrations of commercial HS from Aldrich.

Keywords: imidazolinone; herbicides; photochemical; SH.

Com. 35
Pesticide analysis and Environment.

SPME, a multi-media sampling method.

Michel MONTURY and Louise URRUTY

EPCA-LPTC, Université Bordeaux 1 CNRS UMR 5472, BP 1043, Périgueux (France)

[e-mail]
Because of the large use of pesticides in our modern societies, and not only for agriculture, these organic compounds must now be considered as constituents of the first importance in all the compartments of our Environment. Whatever the observed medium is, concentrations of these biocides have now reached such a level that their rigorous determination in every natural matrix has become a real need for studying their effect on human health and then, an important challenge for analytical chemists.
Recent developments of the Chromatographic Science are now providing reliable methods and techniques for analysing most of these molecules in a routine mode, at the level of few µg L^-1 and sometimes less, but provided these analytes being chromatographied from organic solvent solutions. Now, natural samples are mainly from aqueous or gaseous matrices, and this means that current methods oblige chemists to operate an organic solvent extraction in a previous step of the analysis. Limits of this approach are well known in terms of analysis duration, solvent pollution, analysis cost and operator technicality.
In the early nineties, the so called Solid Phase Micro-Extraction (SPME) technological approach, proposed by J. Pawliszyn [1] and his group, has induced the development of a large number of simple and not expensive sampling methods, allowing the uptake of a thermodynamically representative aliquot of the analytes directly from the natural sample and without the use of any organic solvent. Rare and precious are such general technologies that can be applied for pesticide analysis of a so large scope of Environmental matrices, not only aqueous as wines [2] or solid as fruits and vegetables [3], but also gaseous as atmospheric air samples [4]. And the list of potential applications is far to be closed….

References:

[1] J. PAWLISZYN, Solid Phase Micro-Extraction: Theory and Practice, Wiley-VCH, New York, 1997.

[2] L. URRUTY and M. MONTURY, Journal of Agricultural and Food Chemistry, 45 (1997) 1519-1522.

[3] C. FALQUI CAO, Z. WANG, L. URRUTY and M. MONTURY, Journal of Agricultural and Food Chemistry, 49 (2001) 5092-5097.

[4] A. SANUSI, F. FERRARI, M. MILLET and M. MONTURY, Journal of Environmental Monitoring, (submitted for publication).

Com. 36
PESTICIDE RESIDUES ON RAISINS IN TURKEY
U.KAYA, M. ERKAN, F. O. ALTINDISLI, R. ALTINCAG, A. U. DURU
Plant Protection Research Institute, Bornova/IZMIR/TURKEY
The amount of pesticides in food at harvest must fall into established tolerances for obtaining safety food. The pesticide residue level in food at harvest can change according to the application dosage and preharvest intervals of pesticides. The pre-harvest intervals of pesticides on grape have been determined under the field conditions. Drying affects pesticide residue levels. On considering one kg of dried grapes (raisins) is obtained from four kg grapes, it is obvious that the residue on raisins theoretically would be four times more than that of grapes.
This study was carried out to determine the residues of bromopropylate, imazalil, iprodion, parathion-methyl, phosalone, procymidone and propargite on raisins. Grape samples were collected after recommended pre-harvest intervals of applied pesticides. Having been dried under sunlight, they were analysed.
As a result of analyses, imazalil residue on raisins 3 days after the last treatment and parathion-methyl residue 14 days after the last treatment were found as 1.6 ppm and <0.03 ppm, respectively. The residues of iprodion and phosalone 15 days after last treatment were 0.51 ppm and 2.75 ppm and procymidone, propargite and bromopropylate residues 21 days after treatment were 1.66 ppm, <1 ppm and 6.89 pmm, respectively. The tolerances of the pesticides on raisins have not established yet in Turkey and in most of other countries. However, the countries that have not tolerances of pesticides on raisins have evaluated pesticide residue using that of grape. It seems to be a residue problem on raisins if we use tolerances of grape instead of raisins. According to this project results, there is not any residue problem on raisins for imazalil, iprodione, parathion methyl and propargite. However, there is a residue problem on raisins for bromopropylate, phosalone and procymidone although there was not a problem on grape on using recommended pre-harvest intervals. This study showed that the pesticide tolerances on raisins should immediately be established for making exact decision.