Interval of essential oil application on tomato bacterial leaf spot control

摘要

Tomato bacterial leaf spot, caused by Xanthomonas spp., can cause significant losses in the crop production. Disease control is difficult and alternative products should be evaluated. Therefore, the objectives of this study were to evaluate Xanthomonas spp. growth inhibition in vitro and to assess the interval of essential oil application on tomato bacterial leaf spot control. To evaluate the growth inhibition halo for Xanthomonas spp. in vitro , clove ( Syzygium aromaticum ) and lemon balm ( Melissa officinalis ) essential oils were used, as well as Tween 20%, copper hydroxide and water. For bacterial leaf spot control, tomato plants were initially sprayed with those products; three days later, the plants were inoculated by spraying with a bacterial suspension (10 7 CFU mL -1 ), and at each interval of 3, 6, 9 or 12 days, the plants were sprayed again with the products. Disease severity was assessed by calculating the area under the disease severity progression curve. Essential oils of clove and lemon balm, and copper hydroxide, at the concentrations of 100 and 10%, inhibited the growth of Xanthomonas spp. in vitro . Similarly, the essential oils reduced the severity of tomato bacterial leaf spot when applied at three- and six-day intervals, showing to be promising in disease control.