Nanocrystals spraying interval for the control of tomato bacterial spot caused by Xanthomonas hortorum pv. gardneri

ABSTRACT Tomato bacterial spot caused by Xanthomonas hortorum pv. gardneri triggers significant losses in crop production, and the active ingredients availability for disease control is limited. For this reason, there is a great demand for plant protection alternatives, such as the use of nanocrystals. Thus, the aim of this work was to evaluate the performance of nanocrystals spraying intervals for the control of tomato bacterial spot. Tomato plants of cv. Santa Cruz Kada were sprayed at 3-4 leaf stage under greenhouse conditions with ZnO:1Mg, ZnOCl, and ZnOCl:0.1Cu nanocrystals, copper and water. Three days later, the plants were inoculated with a bacterial suspension (109 CFU mL -1). Then, after 3, 6, 9, or 12-day intervals, the plants were sprayed with the products. The bacterial spot severity was periodically quantified as affected leaf area percentage, and the area under the disease progress curve was calculated. Nanocrystals ZnO:1Mg, ZnOCl, and ZnOCl:0.1Cu reduced the tomato bacterial spot severity when sprayed at 3- and 6-day intervals. Thus, nanocrystals may be used for the tomato bacterial spot control when sprayed at 6-day intervals, once this interval is adequate and practical for disease management.