Efficacy of pre-emergence herbicides in controlling Sumatran fleabane (Conyza sumatrensis) in the off-season

F.C. Garcia¹, A.J.P. Albrecht², L.P. Albrecht², J.R. Barbosa¹, A.F.M. Silva³*, W.F. Larini⁴, G. Moreno² and A.A.M. Barroso⁴

¹State University of Maringá (UEM), Department of Agronomic Sciences,
Estrada da Paca, BR87502-970 Umuarama, PR, Brazil
²Federal University of Paraná (UFPR), Department of Agronomic Sciences, R. Pioneiro 2153, BR85950-000 Palotina, PR, Brazil
³Crop Pesquisa, Linha Bem-ti-vi, BR85955-000 Maripá, PR, Brazil
⁴UFPR, Department of Crop Science and Plant Health, R. dos Funcionários 1540, Curitiba, PR, Brazil
*Correspondence: afmoreirasilva@alumni.usp.br

Abstract:

Pre-emergence herbicides can be effective in controlling Sumatran fleabane
(Conyza sumatrensis [Retz.] E.Walker) at soybean and other crops. The goal was to evaluate the effectiveness of sulfentrazone/diuron, imazethapyr/flumioxazin, flumioxazin, diclosulam, s-metolachlor, imazethapyr, clomazone and imazapic/imazapyr in controlling Sumatran fleabane for application in the off-season before soybean planting. Three experiments were conducted in the off season, with 9 treatments. The control of Sumatran fleabane was evaluated at 28, 42 and 49 days after application (DAA), at 49 DAA was performed counting of plants per m². In experiment 1, the worst performance was found for s-metolachlor (58.3% final control), in a situation of lower emergence flow of Sumatran fleabane, with equivalence for the other herbicides. In experiments 2 and 3, with greater emergence flow of Sumatran fleabane, clomazone efficacy stood out (≥ 86.3% final control). A micro-encapsulated formulation of clomazone was used, which causes greater intoxication to this weed due to its slow release into the soil, and presents less loss to the environment. In conditions of lower emergence of Sumatran fleabane, sulfentrazone/diuron, imazethapyr/flumioxazin, flumioxazin, diclosulam, imazethapyr, clomazone and imazapic/imazapyr were effective in controlling it. Even in this condition, s-metolachlor was not effective in controlling Sumatran fleabane. The application of clomazone was effective in controlling Sumatran fleabane in the three experiments. Clomazone is characterized as an important herbicide for use in the off season in the management of this weed before soybean sowing.

Key words:

clomazone, early management, Erigeron sumatrensis, weed, weed emergence