Efficiency of some commercial stimulants in inducing Tomato resistance to Tetranychus urticae (Acari: Tetranychidae)

The effect of some commercial stimulants on inducingresistance in tomato cultivars K186 F1and 023 F1to two-spotted spider mites (Tetranychus urticaeKoch) was evaluated. The experiment was conductedunder open-field conditions during the 2017 and 2018 summer seasons. Stimulants were applied to field-grown tomato plants after observingT. urticaeindividuals. The population of the movable stages of T. urticaeat the start of the application and weeklyintervals was counted as a measure of plant resistance. The initial population at three weeks after transplanting on both cultivars was within the economically safe range (<1 mite/leaflet) for both seasons. The population of T. urticaeincreasedgradually with plant age. The applied stimulants delayed the arrival of the economically significantdamage until the 11 weeks after transplanting, especially with the spraying of Silical® (45% silicon oxide, 9% calcium, and 0.9% boron) and Stansh® (35% siliconoxide, 11.5% potassium oxide, and 13.4% silicon). The density of glandular and non-glandular trichomes on tomato leaves for various treatments was assessed at 13 weeks after transplanting. The stimulants had a significant positive effect on trichomedensity.The highest densities were found with Silical®, Stansh®,and Ultrafit® (38% salicylicacid, 2.8% nitrogen, 6.2% phosphor, and 23% potassium) for both cultivars. The foliar essential oil in Silical®, Ultrafit®, and control treatments was analyzed using theGC-MS technique. Silical® and Ultrafit® spraying stimulated tomato leaves to synthesize compoundsthat have acaricide activity. Chlorfenapyr was synthesized in both cultivars,and 2-dehydro-1,8-cineole, -gurjunene, -humulene, and heptacosaneweresynthesized in cultivar 023 F1. Silical® and Ultrafit® spraying also increased the synthesis of some monoterpenoids that helped tomatoesresist T. urticae. Induced tomato resistance doesnot eliminate pest problems, but helpsreduce pest populations and damage below the economic threshold. Silicon compounds can be accepted as part of integrated pest management, which must be carefully chosen for long-term agricultural sustainability.