Tomato bacterial spot caused by four species of Xanthomonas can cause significant losses to the crop production, and the use of silicon in the protection of plants tend to reduce the disease incidence. The aim of this study was to evaluate silicon sources on the control of tomato bacterial leaf spot. To evaluate the in vitro bacterial growth inhibition, sterile paper discs containing 10 µL of colloidal silicon or potassium silicate were used at the concentrations of 10, 30, 40 and 50 µg µL-1. These discs were placed over the bacteria grown on Petri dishes containing culture medium, and the formation of inhibition zones was observed. To evaluate the reduction in the severity of tomato bacterial leaf spot in greenhouse, tomato plants were sprayed with the products at the concentrations of 10, 20, 30, 40 and 50 g L-1 and, after three day, spray inoculation of the bacterial suspension (109 CFU mL-1) was done. Control treatments consisted of plants sprayed with distilled water or inoculated with the bacterial suspension. Colloidal silicon was not effective in controlling Xanthomonas spp. Potassium silicate, at the concentrations of 30, 40 and 50 µg µL-1, inhibited the in vitro bacterial growth and, at the concentrations of 40 and 50 g L-1, reduced tomato bacterial leaf spot disease.
Potassium silicate; Xanthomonas euvesicatoria; X. gardneri; X. perforans; X. vesicatoria
