The aim was to evaluate the selectivity and weed control of herbicides atrazine, nicosulfuron, mesotrione and tembotrione, applied alone and associated, in post-emergence of maize. Were carried out two experiments, one in the field in a randomized complete block design with four replications and eleven treatments, the second in greenhouse in a completely randomized design, with four replications and ten treatments. The treatments were composed of isolated and associated herbicides. Treatments were applied V4 stage of plants. For first experiment, crop injury and control evaluations were performed, as well as variables related to agronomic performance (plant height, ear insertion height, prolificacy index, yield and mass of 1,000 grains) and mass of weeds. For second experiment, evaluations of crop injury, height, diameter and dry mass of plants were performed. The lower yield for experiment one was verified in the treatment where only mesotrione was applied, which was attributed to the lower control of monocotyledons weeds. Crop injury were observed at 21 DAA in both experiments, but not exceeding 7.5%. All treatments were considered selective to maize. The herbicides atrazine, nicosulfuron, mesotrione and tembotrione, at associations, were effective in the weed control, except the association atrazine + mesotrione.

-The presence of weeds and nematodes can affect of sugarcane yield. This research evaluated whether weeds that are very frequent in mechanized harvested sugarcane can be hosts for root-knot nematodes: Meloidogyne incognita or Meloidogyne javanica. Regarding nematode hospitability, ten weed species as well as a control sample (tomato) were evaluated; they were inoculated with M. incognita and M. javanica. The plants were inoculated with 2,000 eggs and second-stage juveniles (J 2 ), and there were three plants per experimental unit (6,000 eggs and J 2 per pot -repeatition); 60 days after inoculation (DAI), the plants were removed and evaluated according to reproduction factor (RF), nematode final population (FP) and reproducibility index (RI). Regarding weed hospitability, it was found that Luffa aegyptiaca acted as a host for both nematodes, with RF > 1, which was higher than the control sample. Digitaria horizontalis was classified as a host for M. incognita and as a non-host for M. javanica. Mucuna aterrima and Crotalaria spectabilis presented the lowest RF and FP. Ricinus communis and Ipomoea triloba presented galls when inoculated with M. incognita, but were not considered host, since they presented RF < 1. None of the weed species was considered immune, i.e., with RF = 0. The lowest RF values of M. incognita (race 3) were related to Crotalaria spectabilis and Euphorbia heterophylla plants. This demonstrates the ability of crotalarias in decreasing nematode population in the field and justifies its use in several areas before planting main crops. Keywords

Soybean DAS-44406-6 (Enlist E3) is tolerant to glyphosate, 2,4-D and glufosinate. However, more information is needed on selectivity of 2,4-D choline on Enlist E3 soybean, alone or in mixtures. The aim of this study was to evaluate herbicide effects on agronomic performance and chlorophyll indices of soybean. Glyphosate was applied at different stages of development of Enlist E3 and RR soybean. Furthermore, 2,4-D choline alone and in mixture with glyphosate or glufosinate were also applied on Enlist E3 soybean. Studies were conducted in 2016/17 and 2017/18 seasons. Experiment 1 consisted of application of glyphosate. The treatments were arranged in a 2x4 factorial (genotpes x growth stage). For genotypes, Enlist E3 and RR were used. For growth stage, control (without application), V4, V6 and R2 were used. Experiment 2 consisted of application of 2,4-D choline, glyphosate, glufosinate and associations, at V4 of Enlist E3 soybean. Crop injury, chlorophyll indices and agronomic performance were evaluated. The equivalent selectivity of glyphosate for Enlist E3 and RR soybean was verified, regardless of the stage. 2,4-D choline, alone or in mixtures, did not reduce chlorophyll indices and yield of Enlist E3 soybean after application at V4. Enlist E3 soybean was found to be tolerant to 2,4-D choline, glyphosate and glufosinate. The results showed that, in addition to glyphosate, Enlist E3 soybean may be an alternative for glyphosate resistant weeds

There is little information on the efficacy and selectivity of sulfonylureas, isolated and in association with glyphosate, in glyphosate and sulfonylurea-tolerant soybeans. Thus, the present study aims to evaluate the efficacy of weed control and selectivity of sulfonylureas, isolated and in association with glyphosate, at post-emergence (V4) of RR2/STS soybean. The experiments were conducted in the in areas located in Piracicaba City, São Paulo State (SP), Brazil (experiment I) and Palotina City, Paraná State (PR), Brazil (experiment II). Treatments were composed of application of the herbicides sulfometuron, chlorimuron, halosulfuron, ethoxysulfuron and glyphosate, isolated and in association, in the BMX Garra RR2/STS cultivar. Experiment I was conducted focusing on the evaluation of the efficacy of weed control; whereas experiment II focused mainly on the evaluation of herbicide selectivity. The experimental design was the randomized complete block, with four replications. Crop injury, weed control, and variables related to agronomic performance were evaluated. Data were submitted to analysis of variance, and the means of the treatments were compared with the Tukey test. Sulfonylureas in association with glyphosate were effective in weed control and selective for the BMX Garra RR2/STS soybean cultivar. The sulfometuron + chlorimuron + glyphosate association presented phytotoxic potential for the BMX Garra RR2/STS cultivar.

A espécie Cyperus rotundus está entre as plantas daninhas mais difíceis de controlar, podendo causar elevados prejuízos na cultura da cana-de-açúcar. As práticas adotadas garantem os valores de produtividade, dentre elas, está o manejo de plantas daninhas. O objetivo deste trabalho foi avaliar o crescimento inicial de mudas pré-brotadas de cana-de-açúcar submetidas à aplicação de herbicidas em pré ou pós-plantio. Foram conduzidos dois experimentos (pré e pós-plantio) em casa-de-vegetação, em delineamento inteiramente casualizado, com quatro repetições. Os tratamentos correspondem aos herbicidas aplicados em três doses em pré-plantio: sulfentrazone (400, 800 e 1.600 g i.a. ha-1), diclosulam (96,6; 193,17 e 386,34 g i.a. ha-1), imazapic (66,5, 133 e 266 g i.a. ha-1) e imazapyr (250, 500 e 1.000 g e.a. ha-1) e pós-plantio: ethoxysulfuron (67,5, 135 e 270 g i.a. ha-1), halosulfuron (56,25, 112,5 e 225 g i.a. ha-1), 2,4-D (670, 1.340 e 2.680 g e.a. ha-1) e MSMA (987,5, 1975 e 3.950 g i.a. ha-1). Além de duas testemunhas sem aplicação de herbicidas. Foram avaliados os sintomas de injúrias, altura, diâmetro, número de folhas, número de perfilhos, teor de clorofila, área foliar, matéria seca da parte aérea e raiz. Os herbicidas em pós-plantio foram considerados seletivos, uma vez que os sintomas de injúrias foram baixos e os outros parâmetros avaliados não foram diferentes da testemunha. Para as aplicações em pré-plantio foram observados sintomas de injúrias até os 60 dias após a aplicação (DAA) para sulfentrazone.

O uso de mudas pré-brotadas (MPB) de cana-de-açúcar é uma tecnologia que proporciona sanidade, vigor e uniformidade de plantio com foco na qualidade e produtividade, para a formação de viveiros e replantio de áreas comerciais, assim como em áreas de MEIOSI. Contudo, a presença de plantas daninhas pode afetar a produtividade por competir por água, luz, nutrientes e espaço com as mudas de cana-de-açúcar. A integração dos métodos cultural, mecânico e químico proporciona o controle das plantas daninhas, de modo que não afetem a produtividade e longevidade do canavial. O controle mecânico através da operação de quebra-lombo associado ao controle químico é uma das ferramentas utilizadas. Assim como o controle químico que através dos herbicidas residuais garantem controle das plantas daninhas durante o estabelecimento da cultura no campo. Contudo, as mudas de cana-de-açúcar possuem raízes que ficam em contato com o herbicida na camada de solo tratada, afetando a questão da seletividade. Dessa forma, o manejo de plantas daninhas no sistema de plantio com MPB proporciona um campo de novos estudos e discussões.

O uso de mudas pré-brotadas (MPB) de cana-de-açúcar é uma tecnologia que proporciona sanidade, vigor e uniformidade de plantio com foco na qualidade e produtividade, para a formação de viveiros e replantio de áreas comerciais, assim como em áreas de MEIOSI. Contudo, a presença de plantas daninhas pode afetar a produtividade por competir por água, luz, nutrientes e espaço com as mudas de cana-de-açúcar. A integração dos métodos cultural, mecânico e químico proporciona o controle das plantas daninhas, de modo que não afetem a produtividade e longevidade do canavial. O controle mecânico através da operação de quebra-lombo associado ao controle químico é uma das ferramentas utilizadas. Assim como o controle químico que através dos herbicidas residuais garantem controle das plantas daninhas durante o estabelecimento da cultura no campo. Contudo, as mudas de cana-de-açúcar possuem raízes que ficam em contato com o herbicida na camada de solo tratada, afetando a questão da seletividade. Dessa forma, o manejo de plantas daninhas no sistema de plantio com MPB proporciona um campo de novos estudos e discussões.

Metsulfuron is widely used for weed management; however, the residual effect on STS soybean cultivars is unknown. The objective of this work was to evaluate the residual effect of the herbicide metsulfuron on the BMX Garra RR2/STS and M 6410 IPRO (non-STS) soybean cultivars. The herbicide metsulfuron was applied at a rate of 2.4 g a.i. ha-1, in pre-planting of soybean plants. The design was completely randomized in a 2×5 factorial scheme with four replications (first factor: two soybean cultivars - STS and no-STS; second factor: five periods between metsulfuron application and soybean sowing - 0, 15, 30, 45, and 60 days). At 7, 14, 21, and 28 days after sowing (DAS), an emergency evaluation of the soybean seedlings was performed; at 28 DAS, height and dry mass of the shoot were evaluated. The height averages for the STS cultivar were higher than the values of the no-STS cultivar. The average dry mass of soybean plants was higher in the STS cultivar at 0, 15, and 30 days between application and sowing. No differences were observed between the cultivars for the periods of 45 and 60 days, for average dry mass. The BMX soybean cultivar Garra RR2/STS was potentially tolerant for the pre-sowing application of the herbicide metsulfuron. The cultivar of M 6410 IPRO (nonSTS) was affected in its initial development by the metsulfuron application during the pre-emergence stage; however, the 60-day metsulfuron application was safer, and therefore, it is recommended to perform the herbicide application in that interval.