S. DERRIDJ, I. ARNAULT, F. MULLER, P. COUZI
INRA, Unité de Phytopharmacie et des Médiateurs Chimiques, Route de St Cyr, 78 026 Versailles, France.

The ovipositional habits of an insect are critical to the survival of the progeny.  During the period of egg laying, D.v.v. females may be present in the maize fields without feeding. Their abundance in fields follows the maize growth stages. The behavioral events leading insect to egg laying are mediated to a large extent by chemical cues. Maize volatiles emitted by silks, kernel, husk attract D.v.v. females. Chemical stimuli which induce D.v.v. acceptability of plant and laying eggs at its bottom are not known.

Our hypothesis is that plant metabolites present on the maize surface through leaching could stimulate oviposition of D.v.v. and explain maize growth stage discrimination.

We collected maize surface water leaches from two hybrids Borbala and LG 2447 grown in green houses at different growth stages on several organs. Soluble carbohydrates and free amino acids were analyzed. Leaches were tested on oviposition in no choice condition on single wild Hungarian females. Oviposition substrate was nylon cloth impregnated with maize leaches and dried in air flux.

Quantities and proportions of primary metabolites on the maize surface discriminate the growth stages, and also the different organs from each others. Maize leaf surface leaches stimulates D.v.v. oviposition. The stimulation is correlated with metabolite composition. Reproductive period of maize is particularly stimulant.

Still no firm conclusions can be drawn about the activity of each primary metabolite, and its influence when isolated or associated in a pattern.

Acknowledgements to co-workers of the European project present in Hungary.