Impact of foliar application of silicic acid on aphid population growth, gas exchange parameters and yield of rapeseed

Silicon (Si) enhances plant resistance against herbivores and improves crop yield. This study investigated the effect of foliar application of silicic acid (SA), an important available form of Si, on the population growth of aphids (Lipaphis erysimi), gas exchange parameters and yield of rapeseed. The first experiment with treatments of foliar spray of 0.4% SA and a control, revealed a significant reduction in L. erysimi population growth in the 0.4% SA treatment (235.60 aphids/ plant) compared to the control (311.16 aphids/ plant). Additionally, the 0.4% SA treatment significantly enhanced rapeseed yield, with 68.28 siliqua per plant, 15.16 seeds per siliqua and 3.73 g yield per plant, compared to the control with 56.08 siliqua per plant, 13.08 seeds per siliqua and 3.26 g yield per plant. The second experiment with treatments of 0.4% SA alone, aphid alone, 0.4% SA + aphid and a control, showed no significant changes in gas exchange parameters for 0.4% SA and the control. However, 0.4% SA + aphid and aphid alone treatments significantly reduced the gas exchange parameters. Notably, 0.4% SA + aphid exhibited a lesser reduction in photosynthetic rate and stomatal conductance compared to aphid alone treatment, indicating the role of SA in enhancing gas exchange parameters during L. erysimi infestation in rapeseed. These findings suggest the beneficial application of SA in rapeseed to reduce aphid infestation, increase gas exchange parameters and improve yield.