As estratégias de manejo de Conyza spp na dessecação pré-semeadura da soja também são eficientes para o controle de Richardia brasiliensis Gomes com associação de inibidores da protoporfirinogênio oxidase (PPO)?

Abstract

Richardia brasiliensis (white-eye) is a difficult-to-control weed of the Rubiaceae family that is tolerant to glyphosate. Its growth is prostrate, making post-emergence control of the crop difficult. The objective of this study was to use the main management methods for controlling Conyza spp. and verify whether they are effective for controlling R. brasiliensis with the association of herbicides that inhibit PPO. For this purpose, three field experiments were conducted at the Experimental Farm of Agricultural Sciences of UFGD. The experiments were conducted in a randomized block design with 9 treatments plus 1 control with 4 replications. Experiment I was based on the following management: (1) triclopyr-butolytic (1020 g a.i. ha-1) + glyphosate (1440 g a.i. ha-1) with sequential glufosinate-ammonium salt (504 g a.i. ha-1) (the other treatments were combinations with PPO herbicides; there was no variation in the doses of g a.i. ha-1 for the same herbicide in different combinations), (2) triclopyr-butolytic + glyphosate with sequential glufosinate-ammonium salt + carfentrazone-ethyl (30 g a.i. ha-1); (3) triclopyr-butolytic + glyphosate with sequential glufosinate-ammonium salt + saflufenacil (49 g a.i. ha-1); (4) triclopyr-butolytic + glyphosate with sequential glufosinate-ammonium salt + flumioxazine (50 g a.i. ha-1 ); (5) triclopyr-butolytic + glyphosate with sequential glufosinate-ammonium salt + thiafenacil (118.65 g a.i. ha-1); (6) triclopyr-butolytic + glyphosate + carfentrazone-ethyl with sequential glufosinate ammonium salt; (7) triclopyr-butolytic + glyphosate + saflufenacil with sequential glufosinate-ammonium salt; (8) triclopyr-butolytic + glyphosate + flumioxazine with sequential glufosinate-ammonium salt; (9) triclopyr-butolytic + glyphosate + thiafenacil with sequential glufosinate-ammonium salt; and (10) control. In experiments II and III, the base managements were, respectively: diclosulan + halauxifen-methyl (31.9 + 6.325 g a.i. ha-1) and mesotrione + atrazine (60 + 600 g a.i. ha-1 ), the remaining associations were the same as in experiment I. Visual control evaluations were conducted at 7, 14, 21, 28, 35, 42, and 49 DAAi and, after sequential application, green pixels were quantified using ImageJ® computer software at 21, 28, 35, 42, and 49 DAAi. At 49 DAAi, the dry matter of R. brasiliensis regrowth, R. brasiliensis seedlings and total seedlings present in the square (0.25 m2 ) was quantified and obtained, as well as the control efficiency of these variables. The results show that the management strategies for Conyza spp. were efficient for the control of R. brasiliensis. Initially, the associations of PPO herbicides enhanced the initial control, especially when associated with thiafenacil, flumioxazine and saflufenacil in the three experiments. For green pixel and dry matter, a residual effect was observed in the treatments flumioxazine, halauxifen-methyl + diclosulan and saflufenacil. The management system proved to be viable for the control of R. brasiliensis, highlighting the need to use herbicides with residual effect to avoid new emergence flows of R. brasiliensis.