EN QUOI L'ETUDE DE L'EPIDEMIOLOGIE DES MALADIES A BEGOMOVIRUS DE LA TOMATE PEUT-ELLE AIDER A LA CONCEPTION DE SYSTEMES DE CULTURE INNOVANTS ?

In the late 1980's, a new biotype of the whitefly Bemisia tabaci and associated begomoviruses appeared in the Caribbean particularly on tomato crops. The propagation of these diseases was supported by the intensification in vegetable cropping systems. The use of insecticides is not efficient, and no resistant varieties are available for these regions. The challenge is to develop integrated pest management packages, adapted to the different contexts. In order to identify the key-factors of the epidemics, we carried out surveys in tomato producing areas. On the other hand, we monitored the begomovirus inoculum pressure and vector populations, we prospected among weeds as virus reservoirs and we evaluated the effect of cultural practices on the disease progress. The survey underlined the great diversity of cultural practices, and revealed some factors linked with low disease incidences : presence of physical barriers, and presence of plants non-hosts of the vectors close to the plots. Tomato is the only reservoir of tomato begomoviruses and the vectors feed mainly on vegetable crops. The epidemic risk is high from March to September and the proximity with an infected plot as well as a high inoculum pressure during the first 3 weeks of culture can cause severe epidemics. Barriers around a plot may delay the epidemic process and reduce the incidence only when vector population level is low. Actually, the control of the disease must be laid on the spatial and temporal management of plots and the elimination of begomovirus sources. The acceptability of these practices needs the demonstration of their impact and a certain level of organisation of the growers for their application