In vitro sensitivity of Xanthomonas vasicola pv. vasculorum and the control of bacterial leaf streak of corn with copper oxychloride alone and in mixtures with mancozeb and fluxapyroxad
2022
Duin, Izabela Moura | Forasteiro, Thayná Aparecida | Rodrigues, Vanessa Hitomi Sugahara | Balbi-Peña, Maria Isabel | Júnior, Rui Pereira Leite
The importance of bacterial leaf streak (BLS) of corn caused by Xanthomonas vasicola pv. vasculorum (Xvv) has been increasing worldwide and there are no studies on its chemical control. The aim of this study was to determine the in vitro sensitivity of Xvv isolates to different chemicals and to evaluate the control of BLS under greenhouse conditions. Tests were carried out with chemicals based on copper oxychloride, copper oxychloride + mancozeb and copper oxychloride + fluxapyroxad and also in combinations with imulsionable mineral oil. For the in vitro test, the chemicals were added to nutrient agar culture medium at the dosages of 1, 5, 10, 20, 50, 100, 200 and 400 μg mL⁻¹ of metallic copper. Aliquots of 5 μL of 10⁸ CFU mL⁻¹ bacterial suspension were placed on the culture medium and incubated at 28 °C. In vitro treatments with copper oxychloride + fluxapyroxad showed bacterial growth inhibition starting from 20 μg mL⁻¹; and for copper oxychloride + mancozeb and copper oxychloride from 50 μg mL⁻¹. The control of BLS under greenhouse conditions was evaluated on corn plants at the V3 phenological vegetative stage sprayed with the chemicals. The corn plants were inoculated with a 10⁸ CFU mL⁻¹ suspension of a Xvv strain. Copper oxychloride + mancozeb and copper oxychloride were the most effective products to control corn BLS. However, symptoms of phytotoxicity were observed in the plants that received applications of these products in the tested dosages of 2 to 5 mL L⁻¹.
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