Efficacy of Control of Glyphosate-Tolerant Species of the Rubiaceae Family Through Double-Knockdown Applications

Eficácia do Controle de Espécies Tolerantes ao Glifosato da Família Rubiaceae Através de Aplicações em Golpe Duplo

A. KALSING C.V.S. ROSSI F.R. LUCIO G.B. MINOZZI F.P. GONÇALVES R. VALERIANO About the authors

ABSTRACT:

Spermacoce latifolia, S. verticillata, and Richardia brasiliensis (family Rubiaceae, tribe Spermacoceae) are glyphosate-tolerant weeds in the soybean producing areas of Brazil. The weed shifts to glyphosate-tolerant weeds across soybean-producing areas has shown the need for adoption of practices that conserve the efficacy of glyphosate. This study evaluated the effect of single- and double-knockdown herbicide applications on the control of S. latifolia, S. verticillata, and R. brasiliensis prior to soybean sowing. Trials were designed as a randomized block and treatments were arranged as a factorial. Factor A was three systemic herbicide treatments 10 days before sowing (DBS), while Factor B was three contact herbicide treatments applied 0 DBS (“sow and apply”). The single- and double-knockdown applications were followed by post-emergence applications of glyphosate or 2,4-D + glyphosate when the crop reached three leaves. The efficacy of control of each weed species was visually evaluated 14 days after sowing (DAS), as well as 0 and 28 days after post-emergence application (DAA). The double-knockdown applications generally provided higher levels of control for the target weeds of the Rubiaceae family than the single-knockdown applications. Glyphosate + 2,4-D, glyphosate + 2,4-D + diclosulam or glyphosate + [halauxifen-methyl + diclosulam] followed by glufosinate or paraquat achieved at least 90% of control of S. latifolia and R. brasiliensis, but did not control S. verticillata (<80%). Glufosinate at 457 g a.i. ha-1 was equivalent to paraquat at 400 g a.i. ha-1 as a contact herbicide in the double-knockdown applications, especially on the first assessment dates.

Keywords:
2,4-dichlorophenoxyacetic acid; ammonium glufosinate; Spermacoce latifolia; Spermacoce verticillata; Richardia brasiliensis

Sociedade Brasileira da Ciência das Plantas Daninhas Departamento de Fitotecnia - DFT, Universidade Federal de Viçosa - UFV, 36570-000 - Viçosa-MG - Brasil, Tel./Fax::(+55 31) 3899-2611 - Viçosa - MG - Brazil
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