Interaction of different nitrogen fertilization regimes of canola with mustard aphid (Lipaphis erysimi Kalt.) and the predatory gall midge (Aphidoletes aphidimyza Rondani)

The host plant quality not only influences on herbivorous insects but also indirectly could impact on their natural enemies’ performance. The current study was conducted to determine the effect of different nitrogen fertilization levels of canola (Brassica napus L.) on life table parameters of the predatory gall midge, Aphidoletes aphidimyza Rondani; Diptera: Cecidomyiidae, in feeding of mustard aphid, Lipaphis erysimi Kalt.; Hemiptera: Aphididae, under controlled temperature (day: 25± 2, night: 19± 2) and humidity (60± 10%) conditions. Mustard aphids were reared on canola plants grown under four nitrogen fertilization levels including 0, 0.055, 0.11, and 0.165 g N. kg soil-1 to produce different prey quality. The developmental time of the predatory gall midge growth stages were recorded daily and life table parameters were evaluated by two-sex life table procedure. The results showed that increased nitrogen fertilization of canola significantly decreased the developmental time of larva and pupa of the predatory gal midge and increased the oviposition period of females. Actually, using high and medium nitrogen fertilization levels improved the performance of the predatory gall midge. In addition, the maximum amounts of net reproduction rate (32.54 offspring per individual) and the intrinsic rate of increase (0.163 d-1) with significant differences were observed in the mediate nitrogen fertilization level (0.11 g N.kg soil-1). So, this level could introduce as the best level for the predatory midge growth.