Silicon derivatives induced host plant resistance against Tetranychus urticae (Acari: Tetranychidae) in eggplants farms

A field experiment was conducted to evaluate the effect of silicon (Si) in the forms of oligomeric silicic acid (OSAB®) and potassium silicate (Silica K®) in inducing the resistance of eggplant Solanum melongena against Tetranychus urticae (Acari: Tetranychidae) infestation. Both forms were applied as a foliar spray at concentrations of 2 mL L−1 and 4 mL L−1, respectively, with three sprays with an interval of 20 days between the three consecutive applications. Tetranychus urticae adult, nymph, and egg counts were recorded 10, 30 and 50 days after spraying (DAS). The effect of the two tested forms on S. melongena defense response was assessed by measuring the activity of enzymatic and non-enzymatic antioxidants. Our results showed that both Si forms at a high concentration (4 mL L−1) significantly decreased the T. urticae stage numbers in S. melongena-treated plants. In addition, the Si-treated plants with the lowest T. urticae infestation were associated with increased Si leaf content, total phenol, and protein contents, as well as increased activity of the antioxidant enzymes compared to the control group. Si leaf content was negatively correlated with the T. urticae population density in S. melongena-treated plants with both tested treatments. In addition, a positive correlation was found between the Si leaf content and the activity of the antioxidant enzymes, total phenol, and protein contents. Applying both Si forms resulted in a positive effect in reducing the T. urticae infestation and its damage to S. melongena. Therefore, Si could be used as a foliar treatment to induce resistance in S. melongena plants, making it a potentially valuable pest management tool.