Persian Journal of Acarology

Abstract The sweet pepper, an important export ‎crop in Egypt, has been recently invaded by the two-spotted spider mite (TSSM) in parallel with other insect pests that have the potential to reduce its yield. This study aimed to determine the susceptibility of two sweet pepper cultivars (cv. Mazurka and Cannon) to TSSM infestation. In addition, it aimed to investigate how the cultivar as well as the growing season, might affect the population fluctuations of the pests along with the host plant resistance. Also, enzymatic and non-enzymatic antioxidant activities were determined to distinguish between the two cultivars after natural infestation. The TSSM was identified as the primary pest that invaded both cultivars during the two examined growing seasons. In addition to the TSSM, three insect pests (Bemisia tabaci, Frankliniella occidentalis, and Myzus persicae) and four predators (Neoseiulus cucumeris, Phytoseiulus persimilis, Scolothrips longicornis, and Orius laevigatus) were identified. The cv. Cannon was found to have the highest density of TSSM, B. tabaci, and M. persicae than cv. Mazurka demonstrated the highest density of P. persimilis and O. laevigatus. Our findings also revealed that the winter-spring season was highly significant in antioxidant enzyme activities than the summer-fall season. Due to the high chlorophyll and phenol contents, and antioxidant enzyme activity in its leaves, the Mazurka cultivar was more resistant to TSSM and other insect pest infestations. The population density of the two-spotted spider mite and the associated pests change based on season and/or cultivar.

Abstract 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.