Manejo químico de buva antes e após infestar a cultura do milho com tecnologia EnlistTM

Abstract

Conyza bonariensis, commonly known as horseweed, causes quantitative and qualitative losses of grains when infesting corn due to competition for water, light, and nutrient between weed and crop. This study aimed to evaluate herbicides’ effectiveness, selectivity, and effects on the physiology and grain yield components of maize with EnlistTM technology. The experiment was conducted in the field using a randomized block design with four replications. The treatments used in early management were glyphosate, glyphosate + atrazine + oil, 2.4 D, glyphosate + 2.4 D, saflufenacil, saflufenacil + glyphosate, and one infested control. Saflufenacil + diquat + oil was used for desiccation before corn sowing. For post-emergence cleaning at the V3 stage of corn, the following herbicides were applied: glyphosate, atrazine + simazine, glyphosate + atrazine + simazine, mesotrione + atrazine, glyphosate + mesotrione + atrazine, atrazine + Smetolachlor, glyphosate + atrazine + S-metolachlor, atrazine + oil, glyphosate + atrazine + oil, 2,4D, dicamba, dicamba + glyphosate, and two more controls, one weeded and the other infested. The control of horseweed was evaluated at 7, 14, and 21 days after herbicide application in early management, seven days after desiccation in maize presowing, and 7, 14, 21, and 28 days after post-herbicide application. Phytotoxicity to hybrid AG 9700 maize with EnlistTM technology was determined at 7, 14, 21, and 28 days. Physiological variables of maize were evaluated 45 days after maize emergence. The components of grain yield, ear length, number of rows, grains per ear, mass of one thousand grains, and grain yield were determined in the maize harvest. The herbicide saflufenacil applied alone and the tank mix of saflufenacil + glyphosate provided the best horseweed controls when used in early management before sowing corn. Saflufenacil + diquat in horseweed desiccation resulted in satisfactory control, mainly when saflufenacil or saflufenacil + glyphosate was applied in early management. The post-emergence application of mesotrione + atrazine, glyphosate + mesotrione + atrazine, and atrazine + oil resulted in the best control of corn buffalo with Enlist™ technology. The herbicides glyphosate, atrazine + simazine, and atrazine + oil showed the lowest phytotoxicity to maize. The application of mesotrione + atrazine and dicamba in the post-emergence of maize caused the best physiological responses of the crop. The use of glyphosate + atrazine + S-metolachlor caused the best effects on the grain yield componentes of corn, including the treatment that showed the highest grain yield.