Dessecação de Conyza spp., em pré plantio da cultura da soja, através de aplicações sequenciais de herbicidas

Abstract

Conyza spp. it is a kind of difficult control, mainly in more advanced phenological stages, demanding specific chemical control strategies. The objective of this work was to evaluate the control of Conyza spp. through an application of the herbicide 2,4-D + glyphosate, followed or not, by sequential applications of desiccant herbicides in isolation and / or associated with pre-emergent herbicides in pre-planting soybean crops. The experiment was carried out in the field in an area with natural infestation of Conyza spp in a randomized block design with 4 replications and 18 treatments. An application of 2,4-D + glyphosate (975 + 1025 g i.a ha-1 ) was carried out and after 15 days of the initial application (DAI) the sequential applications were performed: diquat (400 g a.i. ha-1 ); carfentrazone (30 g i.a ha-1 ); ammonium glufosinate (500 g a.i. ha-1 ); saflufenacil (49 g a.i. ha-1 ) individually and associated with flumioxazin + imazetapyr (50 + 100 g a.i. ha-1 ); sulfentrazone + diuron (245 + 490 g a.i. ha-1 ) and diclosulan (29.4 g a.i. ha-1 ) and the control without herbicide application. A single 2.4 D + glyphosate application is not effective in the control of Conyza spp., At 56 DAT the control was only 25%, emphasizing the need for sequential applications. All treatments that included carfentrazone in the sequential application, did not result in effective control of Conyza spp., With percentages below 70%. All treatments with diquat, saflufenacil and ammonium glufosinate, associated or not with pre-emergent herbicides, diclosulan, sulfentrazone + diuron and flumioxazin + imazethapir, resulted in control percentages greater than 80%. The association of the herbicide diclosulan + carfentrazone in the sequential application resulted in a synergistic effect, since the use of the isolated product provided a control of Conyza spp. of 30% when the association of carfentrazone + diclosulan resulted in a control of 62.5%. It is concluded that the herbicide carfentrazone is not an alternative for the control of Conyza spp., in sequential applications, being that the herbicides diquat, ammonium glufosinate and saflufenacil used alone or associated with pre-emergents (flumioxazin+imazethapyr), (sulfentrazone+diuron) and (diclosulan) are viable for the management of Conyza spp.