Six trials were conducted during 2014/15 and 2015/16 growing seasons in Brazil to determine the effect of 2,4-D formulations and spray nozzles on 2,4-D spray drift under conventional field conditions. An experimental 2,4-D choline formulation with Colex-D® Technology (GF-3073) and a 2,4-D dimethylamine (DMA) formulation were applied with either XR and AIXR flat-fan spray nozzles. Each plot was 30 m wide by 24 m long (720 m2) with 60 glyphosate-resistant soybean rows spaced 50 cm apart and also 35 potted tomato plants distributed on a grid across the plot 5-m apart. Applications were performed one meter away from the plot edge perpendicular to the soybean rows when wind direction was parallel to the rows with less than 30 degrees of angle deviation. Spray drift treatments were applied in 100 L ha−1 with tractor sprayers at 276 kPa equipped with a 7-m wide boom at 50 cm above the canopy of the soybean plant, operating at 6.8 km h−1. The distance from the plot edge to the farthest plant with 2,4-D symptoms was assessed for every four soybean rows at 10 and 20 days after treatment (DAT) and potted tomatoes at 10 DAT. GF-3073 reduced the distance of the farthest injured plant with 2,4-D symptoms compared to the 2,4-D DMA formulation regardless of the spray nozzle, assessment date and sensitive species. GF-3073 applied through the AIXR nozzle reduced the relative drift affected area to the standard by 68% at 10 DAT and 67% at 20 DAT for soybean and 60% at 10 DAT for potted tomatoes.

Soybean stem necrosis is caused by cowpea mild mottle virus (CPMMV), transmitted by the whitefly Bemisia tabaci. CPMMV has already been recorded in all major soybean-producing areas of Brazil. The impacts caused by CPMMV to the current Brazilian soybean production are unknown, thus the main objective of this study was to evaluate the effects of CPMMV infection on the main important soybean cultivars grown in the Southern and Midwestern regions of Brazil. Although asymptomatic in some of the tested cultivars, CPMMV infection significantly reduced the plant height, the number of pods per plant and the 1,000-grain weight. In addition, estimated yield losses ranged from 174 to 638 kg ha−1, depending on the cultivar. Evidence of seed transmission of CPMMV was observed in the BMX POTÊNCIA RR cultivar. These results suggest that CPMMV could have an important role in the reduction of soybean productivity in Brazil, but symptomless infections might be hiding the actual impact of this pathogen in commercial fields and infected seeds could be the primary inoculum source of the virus in the field.

RESUMOO uso contínuo do herbicida glifosato pode selecionar biótipos de plantas daninhas resistentes e exigir o desenvolvimento de novas práticas de manejo. Desta forma, o objetivo da proposta foi avaliar a eficácia de diferentes manejos das plantas daninhas na cultura da soja roundup ready, através de herbicidas residuais e pós-emergentes. O experimento foi instalado no delineamento em blocos ao acaso, com 14 tratamentos e quatro repetições e envolveram a aplicação de diclosulam (29,4 g ia ha -1 ) ou sulfentrazone (600 g ia ha -1 ) em mistura com glifosato (712 g ia ha -1 ) e 2,4-D (670 g ia ha -1 ) na dessecação das plantas daninhas, 14 dias antes da semeadura da soja. Posteriormente, foram feitas aplicações de glifosato em pós-emergência nos estádios de desenvolvimento V2 e V4 (356 g ia ha -1 ) ou glifosato aplicado em uma única vez em V2 ou V4 (712 g ia ha -1 ), além das testemunhas sem herbicida e testemunha sem os herbicidas residuais. Atentou-se para a importância de aplicar herbicida residual junto com o glifosato, tanto do ponto de vista de controle de plantas daninhas como em relação ao desenvolvimento da cultura. A adição dos herbicidas diclosulam ou sulfentrazone à dessecação tornou uma única aplicação de glifosato no estádio V4 da soja suficiente. Palavras-chave: glifosato, inibidores da ALS, plantio direto Residual herbicides in weed management in transgenic soybean ABSTRACTThe continued use of glyphosate can select resistant weeds biotypes and tolerant species, suggesting the need to develop new management practices. Thus, the aim of this proposal was to evaluate the effectiveness of different managements in soybean using residual herbicides and post-emergent control of weeds, and observe the possible effects on crop development. The experiment, in the field, was in a randomized block design with four replications and 14 treatments, involving the application of diclosulam (29.4 g ai ha -1 ) and sulfentrazone (600 g ai ha 1 ) and post emergent glifosato (712 g ai ha -1 ) and 2,4-D (670 g ai ha -1 ) in weed desiccation, 14 days before soybean sowing, and treatments with glifosato in soybean stages V2 and V4 (356 g ai ha -1 ) and glifosato applied at a single time in V2 or V4 (712 g ai ha -1 ). We noted the importance of applying residual herbicides with glyphosate to weed control plant, and for the development of culture. The addition of the herbicide sulfentrazone diclosulam or desiccation became a single application of glyphosate in the V4 stage of soybean enough.

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.

Resumo -O objetivo do trabalho foi avaliar a eficácia de herbicidas aplicados em pré-emergência, em diferentes doses e épocas, antes da semeadura de soja sob condição de déficit hídrico, para o controle de plantas voluntárias de algodão, tolerante aos herbicidas glyphosate e amônio glufosinate,