This study assessed the effect of silicon-based fertilizer treatments on development of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood), while feeding on poinsettia, Euphorbia pulcherrima (Willd. ex Klotzsch). A potassium silicate fertilizer was applied at treatment rates of 0, 50, 100, 400, and 800 ppm silicon as a growing medium drench. The mean development time, proportion (%) of pupae and proportion of T. vaporariorum adult emergence were determined for each assessment period. Total silicon concentration in the aboveground tissues (leaves and stems) of poinsettia plants were measured at 4 time intervals throughout the study, using a plant alkaline fusion technique (PAFT) silicon determination procedure. Total moisture content (g), height (cm), and number of fully-expanded mature leaves of the poinsettia plants also were measured. Our results showed significant differences in silicon concentration with poinsettia plants receiving the 100, 400, and 800 ppm silicon treatments having the highest silicon concentrations (1240, 1193, and 1121 mg kg−1 silicon, respectively) in the aboveground tissues. However, there were no significant differences in development time or emergence rates of T. vaporariorum adults when feeding on poinsettia plants treated with potassium silicate in the nutrient solutions. There also were no significant differences in moisture content (g), height (cm), and number of fully-expanded mature leaves of poinsettia plants associated with the silicon-based fertilizer treatments. Incorporating potassium silicate into nutrient solutions did not confer resistance to T. vaporariorum populations developing on poinsettia leaves, and applications of the silicon-based fertilizer failed to enhance the plant growth parameters measured, height (cm), number of fully-expanded mature leaves, and moisture content (g).

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