THE IMPACT OF NITROGEN-FERTILIZATION OF TOMATO ON FEEDING SITE SELECTION AND OVIPOSITION BY TRIALEURODES-VAPORARIORUM

Tomato plants, Lycopersicon esculentum Miller cv 'Tres Cantos', were s upplied with high (308 ppm), medium (140 ppm) and low (84 ppm) nitroge n doses in order to determine the influence of nitrogen fertilization on feeding and oviposition site selection by greenhouse whitefly adult s, T. vaporariorum (Westwood). The nitrogen and water content was high er in plants supplied with 308 N ppm than in plants with medium or low nitrogen doses and no differences were found in soluble sugar content . The leaves of the upper plant stratum (leaves 1-5) had the greatest nitrogen and water content, independent of the nitrogen dose applied. The plants were exposed to T. vaporariorum adults into a greenhouse un der two current (late autumn-winter and spring-early summer) situation s of the tomato crop in the Mediterranean area. The distribution of wh itefly adults on the plants was affected by the nitrogen dose in both experimental conditions, the number of adults was higher on the plants supplied with high nitrogen dose. Within plants, adult distribution w as affected by leaf position, the upper plant stratum being preferred for feeding. Whitefly females selected for oviposition and laid more e ggs on plants and leaves of plants with higher nitrogen and water cont ents. We conclude that whitefly host selection for feeding and oviposi ting are related to differences in nitrogen and water content of the h ost plant.