Abstract
Silicic acid (SA) is an important source of silicon (Si) that induces resistance in plants against insect pests. The present investigation aimed to investigate the impact of foliar spray of SA on the biological parameters of aphid, Lipaphis erysimi and the activity of defensive enzymes in rapeseed. The results demonstrated applying 0.4% SA significantly reduced the nymphal period, adult longevity and fecundity of L. erysimi compared to the control. In the 0.4% SA- treated rapeseed, the nymphal period, adult longevity and fecundity of L. erysimi were 7.00 days, 7.96 days and 23.52 nymphs/ female, respectively, while in the control, these were 7.92 days, 8.80 days and 26.04 nymphs/ female, respectively. The present investigation revealed that there were no significant changes in activity of defense related enzymes such as peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia- lyase (PAL) in 0.4% SA- treated rapeseed without aphid infestation. However, a significant increase in the activity of these enzymes was observed in rapeseed amended with 0.4% SA that were subsequently infested with aphids. The application of SA significantly increased the Si content in rapeseed. Furthermore, the study established a significant negative correlation between Si content and biological parameters of L. erysimi.