Evaluation the effect of nitrogen fertilization of canola on performance and population growth rate of mustard aphid, Lipaphis erysimi (Hem.: Aphididae)

Variation in host plant quality in response to nitrogen fertilization could influence on performance and population of insect herbivores. Current greenhouse study was conducted to determine the effect of four nitrogen fertilization levels including 0, 75, 150 and 225 kg. ha-1 in canola (Brassica napus L.) on performance and population growth rate of mustard aphid (Lipaphis erysimi Kalt.). The results showed that increasing nitrogen levels had significantly affected the nitrogen content and carbon/nitrogen of canola plants. The maximum percent of leaf-N (3.05±0.09) and minimum ratio of C/N (16.00±0.70) were observed in plants fertilized with the highest nitrogen level. Increasing nitrogen fertilization significantly enhanced aphid performance. The shortest nymphal developmental period (5.76±0.08 days) and the maximum fecundity (95.38±5.03) were observed at the level of 225 kg N.ha-1. Regression analysis showed a positive significant relationship between the intrinsic rate of increase (rm) and nitrogen treatment. The aphids’ rm increased 20.64 % with increasing nitrogen levels from 0 to 225 kg. ha-1. Moreover, the population of mustard aphid significantly was affected by nitrogen treatment and sampling date. The maximum population was observed in 3rd sampling date and in the highest nitrogen fertilization. In all sampling dates, the maximum population growth rate was calculated in the highest nitrogen level. The population growth rate showed a decreasing trend with increasing sampling date.