Effect of nitrogen fertilization level applied to tomato on the greenhousewhitefly

The greenhouse whitefly, Trialeurodes vaporariorum (Westwood), was studied on tomato plants, Lycopersicon esculentum (Miller) treated with three diffe rent nitrogen levels [308, 140 and 84 ppm] within the normal range for toma to fertilisation in Spain. Nitrogen affected the thickness of the leaflet l amina and of the abaxial epidermal cuticle; plants supplied with 308 ppm of N had the thinnest leaf. High nitrogen fertilization increased egg surviva l, size of pupal exuviae and female tibial length. Females that had been re ared on plants fertilized with 84 ppm of N showed the lowest oviposition fr equency, when allowed to oviposit on plants fertilized with 140 ppm of nitr ogen, but the development time of immatures and the longevity and fecundity of the next generation of females were not significantly different. T. vaporariorum populations that developed on plants fertilized with high n itrogen level showed a higher intrinsic rate of increase, making its contro l more difficult. (C) 2000 Published by Elsevier Science Ltd. All rights re served.