Demographic Parameters of Lipaphis erysimi on Canola Cultivars under Different Nitrogen Fertilization Re gimes

Abstract

Increased nitrogen applications to crops influence plant-herbivore interactions and potentially increase herbivore population growth. In this research, the impact of nitrogen fertilizations on nutritional quality of three cano la ( Brassica napus L.) cultivars (Zarfam, Okapi and Modena), and, consequently, the performan ce of mustard aphids, Lipaphis erysimi Kalt., on them were investigated under green house conditions. Nitrogen fertilization treatments were 0, 75, 150, and 225 k g N. ha -1 . The results showed that increased nitrogen fertilization resulted in enhanc ing plant nitrogen content and decreasing of C/N ratio of leaves. Based on N-conte nt and C/N ratio, Zarfam had the highest nutritional quality for herbivore among the tested canola cultivars. Fertilization generally increased the susceptibility of plants to mustard aphid. Therefore, aphids feeding on plants receiving higher nitrogen levels had shorter nymphal developmental time, longer adult longevity as well as greater fec undity. The highest and the lowest values of aphids’ intrinsic rate of increase ( r m ) were calculated on Zarfam and Modena cultivars, respectively. Moreover, nitrogen fertilization posi tively affected r m of aphids on all canola cultivars. According to our results, management of nitrogen fertilization and cultivation of resistant cultivar could be suitable eco-friendl y strategies to manage mustard aphid population. Keywords: Life table parameters, Nitrogen fertilizer, Plant resistance.