Foliar amendment of silicic acid on population of yellow mite, Oligonychus sacchari (Acari: Tetranychidae) and its predatory beetle, Stethorus gilvifrons (Col.: Coccinellidae) on two sugarcane commercial varieties

Sugarcane (interspecific hybrids of Saccharum) is a strategically important cash crop that has an economic and social impact in many countries. Sugarcane mite, Oligonychus sacchari is one of the most detrimental arthropod pests associated with sugarcane during summer. Control of this pest is mainly based on chemical pesticides and cultural practices as well as the application of silicon as a nutritional component of an integrated crop management. In this study, effects of silicon were evaluated on O. sacchari. Experiments were carried out during 2014–2015 and 2015– 2016 at Salman Farsi Agro Industry Farms, Ahwaz-Iran. The two varieties (CP57-614 and CP48-103) were treated by silicic acid fertilizer as foliar application. Five treatments including one spray (0.5 lit/ha), two sprays (0.5 and 1 lit/ha 3 weeks after spray 1), three sprays (0.5, 1 and 1 lit/ha 4 weeks after spray 2), four sprays (0.5, 1, 1 and 1 lit/ha 4 weeks after spray 3) and Control were applied. In each plot, 15 leaves were randomly selected from bottom, mid and top of plant and number of living mites and dry leaves were recorded. Samples were collected 7, 14, 21 and 28 days after the forth application of silicic acid. The results showed that all treatments had significant effects in mite population and leaf dryness versus Control. Among different treatments of silicic acid, four spray application of silicic acid was more efficient than other treatments on mite damage and leaf dryness. It seems that the silicic acid would be a promising product for management of mite damage and could be incorporated with other management strategies in sugarcane IPM.