P. REYNAUD
LNPV Ministere de l'Agriculture - Unite d'entomologie - UFR d'Ecologie animale et de Zoologie agricole ,  2 place Viala - 34060 Montpellier Cedex 01 - France

The development of the Western Corn Rootworm in Eastern Europe and then, the discovery of a small population in Italy are 2 particularly alarming events. The cultivation of corn is very important in France. It represents 1,8 million hectares, that is to say as much as all the bordering countries joined together, The average yield is high (84 quintal / hectare).

One of the missions of the French Plants Protection Service is to avoid the introduction and the spread of pests on its territory and the possible application of phytosanitary measures of control and eradication. For that, a good knowledge of the situation on the area is necessary. Thus> it was decided in 1999 to set up an official monitoring of Diabrotica virgifera by sexual trapping.

Materials and methods
Sixteen locations are selected, by seeking risk situations and/or representative situations of the corn cultivation in France. Several trappings are carried out near international airports or private center of seed corn experimentation. The aim of the study is the detection of early infestations and not the study of population dynamic. So, we have selected a pheromone traps system of PAL type (sticky cloak trap) marketed by the Plant Protection Institute of the Hungarian Academy of Science (MTA Növenyvedelmi Kutatoitezete). Only the male is attracted, sticky surface is colorless to avoid an attractive effect on others insects species.

The traps were put in place at the end of June, i.e. a few days before the first theoretical emergence of adults according to the model. On each site of capture, two traps are installed, to 20-25 meters one of the other. It is a weekly survey.

Results
The observation of the traps, between the end of June and the end of August, did not show any Diabrotica virgifera in France.

Theoretical cycle of Diabrotica virgifera in France
Using software CLIMEX and for 2 situations, an evaluation of the potential cycle of the insect was carried out. This assessment uses the average climate in the long run of the stations of Bordeaux (44,8 N, -0,6 E) and Strasbourg (48,6 N, 7,8 E). The beginning and the end of diapause are calculated by CLIMEX. The date of hatch of eggs is based on a thermal summation (Schaafsma et al., 1991) as for the emergence of adults (Jackson et al. 1988). This simulation shows that the diapause ends between 20th and 30th April.The emergence of the first larvae is foreseen at the end of May in south-west and at the beginning of June in north-east. The first adults are expected, in an average year, between the 5th and the 12th of July.