Interference of glyphosate-resistant conyza sumatrensis in soybean crops in Central Brazil

Background: Studies on losses caused by competition of soybean with Sumatran fleabane plants in the Cerrado biome are scarce and need to be conducted to assist in choosing more effective weed Objective: Evaluate the effect of glyphosate-resistant Sumatran fleabane plants on soybean and describe their dynamics regarding emergence of new plants and mortality of adult plants in the hot summer rainy season Methods: Three field experiments were conducted at the Embrapa Cerrados site (Brasilia, DF, Brazil) over two years, using a randomized block experimental design with ten treatments, six competition periods and four controls, and four replications. The treatments consisted of periods of competition of soybean with Sumatran fleabane plants in the plots: until 10 (0-10), 20 (0-20), 30 (0-30), 45 (0-45), and 60 (0-60) days after soybean sowing (DAS) and until soybean harvest. Four control treatments were used to evaluate the dynamics of Sumatran fleabane and soybean plants, also considering other emerged weed species. Evaluations were carried out on Sumatran fleabane plants and soybean. Results: None of the competition periods negatively affected the establishment and development of soybean. The Sumatran fleabane plant cycle ended from 45 to 60 DAS. Only one Sumatran fleabane emergence period (approximately 24 DAS) occurred throughout the soybean cycle, these plants died due to shading by the crop. Conclusions: Sumatran fleabane plant densities of 13 to 23 plants m-2 at the soybean sowing did not interfere with the crop establishment and development.