Herbicide selectivity in pre-sprouted seedlings of 'CTC14' sugarcane / Seletividade de herbicidas em mudas pré-brotadas de cana-de-açúcar 'CTC14'

A new sugarcane planting system, using pre-sprouted seedlings (PSS) to replace sugarcane stem fragments, substantiates the hypothesis of this study that there might be seedling toxicity by herbicides that are sprayed at pre-emergence in traditional systems. Therefore, the aim of this paper was to study the selectivity of herbicides applied at pre-planting in PSS. A field experiment was conducted in a randomized block design, using seven treatments and four replications. Herbicides were sprayed and, 24 hours later, the seedlings were planted. At the beggining of seedling development, all herbicide treatments showed phytotoxicity, but the symptoms decreased with the growth and development of seedlings, with no difference in height, stem diameter, number of leaves, quantum efficiency of PSII (Fv/Fm) and dry matter of plants between treatments. There was also no significant difference in the yield and technological characteristics of stems. All herbicides used were selective to sugarcane seedlings when applied at pre-planting in the PSS system.(AU)

Um novo sistema de plantio de cana-de-açúcar, utilizando mudas pré-brotadas (MPB) em substituição aos fragmentos de colmos de cana, fundamenta a hipótese deste trabalho de que poderá haver intoxicação nas mudas pelos herbicidas aplicados na pré-emergência em sistemas tradicionais. Portanto, objetivou-se neste estudo verificar a seletividade de tratamentos herbicidas aplicados em pré-plantio de MPB. O experimento foi realizado a campo, em blocos randomizados, utilizando sete tratamentos em quatro amostras replicadas. Foi realizada a pulverização dos herbicidas e, após 24 horas, o plantio das mudas. No início do desenvolvimento das mudas, todos os tratamentos com herbicida causaram fitotoxicidade, mas com o crescimento e desenvolvimento das mudas, os sintomas foram diminuindo, não havendo diferença entre os tratamentos quanto à altura, o diâmetro de colmos, o número de folhas, a eficiência quântica do FII (Fv/Fm) e a matéria seca das plantas. Também não houve diferença significativa na produtividade e nas características tecnológicas dos colmos. Todos os herbicidas utilizados foram seletivos às mudas de cana-de-açúcar no sistema MPB quando aplicados no pré-plantio.(AU)

Herbicide selectivity in pre-sprouted seedlings of 'CTC14' sugarcane / Seletividade de herbicidas em mudas pré-brotadas de cana-de-açúcar 'CTC14'

A new sugarcane planting system, using pre-sprouted seedlings (PSS) to replace sugarcane stem fragments, substantiates the hypothesis of this study that there might be seedling toxicity by herbicides that are sprayed at pre-emergence in traditional systems. Therefore, the aim of this paper was to study the selectivity of herbicides applied at pre-planting in PSS. A field experiment was conducted in a randomized block design, using seven treatments and four replications. Herbicides were sprayed and, 24 hours later, the seedlings were planted. At the beggining of seedling development, all herbicide treatments showed phytotoxicity, but the symptoms decreased with the growth and development of seedlings, with no difference in height, stem diameter, number of leaves, quantum efficiency of PSII (Fv/Fm) and dry matter of plants between treatments. There was also no significant difference in the yield and technological characteristics of stems. All herbicides used were selective to sugarcane seedlings when applied at pre-planting in the PSS system.(AU)

Um novo sistema de plantio de cana-de-açúcar, utilizando mudas pré-brotadas (MPB) em substituição aos fragmentos de colmos de cana, fundamenta a hipótese deste trabalho de que poderá haver intoxicação nas mudas pelos herbicidas aplicados na pré-emergência em sistemas tradicionais. Portanto, objetivou-se neste estudo verificar a seletividade de tratamentos herbicidas aplicados em pré-plantio de MPB. O experimento foi realizado a campo, em blocos randomizados, utilizando sete tratamentos em quatro amostras replicadas. Foi realizada a pulverização dos herbicidas e, após 24 horas, o plantio das mudas. No início do desenvolvimento das mudas, todos os tratamentos com herbicida causaram fitotoxicidade, mas com o crescimento e desenvolvimento das mudas, os sintomas foram diminuindo, não havendo diferença entre os tratamentos quanto à altura, o diâmetro de colmos, o número de folhas, a eficiência quântica do FII (Fv/Fm) e a matéria seca das plantas. Também não houve diferença significativa na produtividade e nas características tecnológicas dos colmos. Todos os herbicidas utilizados foram seletivos às mudas de cana-de-açúcar no sistema MPB quando aplicados no pré-plantio.(AU)

Shoot and root interference of morning glory on the initial growth of sugarcane

ABSTRACT Among weeds, morning glories comprise a very important group of climbing plants that infest sugarcane crops. The objective of this study was to evaluate the shoot and root interference of Merremia cissoides on the initial growth of sugarcane cultivar RB 966928. The experiment consisted of five treatment groups: (i) sugarcane monocropping, (ii) morning glory monocropping, (iii) sugarcane intertwined with morning glory but inseparate boxes, (iv) sugarcane intertwined with morning glory in attached boxes and (v) sugarcane with morning glory in attached boxes with morning glory prevented from intertwining with the sugarcane. The experimental design consisted of randomized blocks with four replicates. Merremia cissoides adversely affected the initial growth of the RB 966928 sugarcane starting at 90 days after transplanting (DAT). This effect increased with the time of intercropping, reaching at 180 DAT with a reduction of 57.3% in height,15.5% in stalk diameter, 90.4% in leaf areas, 86.6 and 75.2% in stalk and leaf dry mass, respectively. These reductions primarily due to the weed intertwining with the sugarcane plants because the weed had a physical choking and shading effect. This negative effect of morning glory on the sugarcane plants increased when they shared the substrate (i.e., when they competed for space and water), which also adversely affected weed growth, reducing 50.2% leaf areas and 42.1% shoot dry mass. The leaf area and the stalk and leaf dry mass of sugarcane are the characteristics more sensitive to the weed interference. Thus, both the shoot and root of M. cissoides interferes negatively in the growth of sugarcane, with the effect proportional to the period of coexistence, highlighting the detrimental effect on the stem (greater economic interest), and may also compromise the mechanical harvesting of the crop.

Shoot and root interference of morning glory on the initial growth of sugarcane.

Among weeds, morning glories comprise a very important group of climbing plants that infest sugarcane crops. The objective of this study was to evaluate the shoot and root interference of Merremia cissoides on the initial growth of sugarcane cultivar RB 966928. The experiment consisted of five treatment groups: (i) sugarcane monocropping, (ii) morning glory monocropping, (iii) sugarcane intertwined with morning glory but inseparate boxes, (iv) sugarcane intertwined with morning glory in attached boxes and (v) sugarcane with morning glory in attached boxes with morning glory prevented from intertwining with the sugarcane. The experimental design consisted of randomized blocks with four replicates. Merremia cissoides adversely affected the initial growth of the RB 966928 sugarcane starting at 90 days after transplanting (DAT). This effect increased with the time of intercropping, reaching at 180 DAT with a reduction of 57.3% in height,15.5% in stalk diameter, 90.4% in leaf areas, 86.6 and 75.2% in stalk and leaf dry mass, respectively. These reductions primarily due to the weed intertwining with the sugarcane plants because the weed had a physical choking and shading effect. This negative effect of morning glory on the sugarcane plants increased when they shared the substrate (i.e., when they competed for space and water), which also adversely affected weed growth, reducing 50.2% leaf areas and 42.1% shoot dry mass. The leaf area and the stalk and leaf dry mass of sugarcane are the characteristics more sensitive to the weed interference. Thus, both the shoot and root of M. cissoides interferes negatively in the growth of sugarcane, with the effect proportional to the period of coexistence, highlighting the detrimental effect on the stem (greater economic interest), and may also compromise the mechanical harvesting of the crop.

Phytotoxicity Study on Bidens sulphurea Sch. Bip. as a Preliminary Approach for Weed Control.

Farmers of the Franca region in Brazil observed that Bidens sulphurea was able to eliminate the Panicum maximum weed, which infected coffee plantations, without affecting the crop. In an effort to determine if the inhibitory effects observed were due to the presence of phytotoxic compounds from leaves and roots, a biodirected isolation and spectroscopic characterization has been carried out. The leaf dichloromethane and root acetone extracts were the most active, and the former appeared to be more phytotoxic to the target species, including four weeds. A total of 26 compounds were isolated from leaves and roots, and four of them are described here for the first time. The major compounds in the leaf extract are the sesquiterpene lactones costunolide, reynosin, and santamarine, and these showed marked inhibition. Amaranthus viridis and Panicum maximum were the most sensitive species of the weeds tested. These three phytotoxic lactones were also evaluated on A. viridis and P. maximum under hydroponic conditions. A. viridis was the most affected species with the three lactones, and santamarine was the most phytotoxic compound on both. This is the first time that the phytotoxicity of sesquiterpene lactones has been evaluated on hydroponic culture. The work described here is a preliminary approach for the use of B. sulphurea for weed control in agriculture, both as a cover crop and by use of its components as natural herbicide leads.

Chemical evidence for the effect of Urochloa ruziziensis on glyphosate-resistant soybeans.

BACKGROUND: Soybean (Glycine max) is an important oleaginous legume that has been cultivated in new areas in Brazil, including pastures. Problems of reduced production yields have been reported by soybean growers when the crop is sown immediately after desiccation of pastures of Urochloa spp. using glyphosate. The objective of this work was to extract, isolate and identify the major chemicals from U. ruziziensis that have phytotoxic activity and to evaluate the possible relation between this effect and reduced soybean yield. RESULTS: U. ruziziensis plants at the flowering stage were desiccated using glyphosate at 1.44 kg ha-1 . The plants were collected between five and ten days after treatment. Extracts of dried and ground shoots were obtained by sequential extraction with hexane, dichloromethane and methanol. The results of wheat coleoptile bioassays indicated that the methanol extract was more inhibitory than the dichloromethane extract regardless of glyphosate application. CONCLUSION: Protodioscin, a steroidal saponin, was isolated from the extract as the major component and the activities of this compound were in good agreement with those found for the extract. The release of this compound into the soil is a plausible explanation for the decrease in production observed in transgenic soybean crop after desiccation of U. ruziziensis. © 2017 Society of Chemical Industry.

Interference periods of velvet bean in sugarcane / Períodos de interferência de mucuna-preta na cultura da cana-de-açúcar

The objective of the present study was to determine the periods of interference of velvet bean on ratoons of sugarcane cultivar 'RB855536' and to identify its potential for decreasing the crop yield and the quality of the harvested product. The experiment was arranged in a randomized block design, with 18 treatments divided into two groups and four replicates per treatment. In the first group, the sugarcane was kept free from velvet bean interference for nine different periods, beginning at bud sprouting: 0-15, 0-30, 0-45, 0-60, 0-90, 0-120, 0-150, and 0-180 days after budding (DAB) and 0-harvest. In the second group, sugarcane was grown in coexistence with velvet bean during the same periods described for the first group. The critical period of interference prevention for velvet bean in ratoons of sugarcane cv. 'RB 855536' lasted 138 days, from 50 DAB (pre-interference period [PIP]) to188 DAB (total period of weed interference prevention [TPIP]). Velvet bean interference caused a 50% decrease in sugarcane yield and negatively affected the quality of the harvested product.(AU)

Objetivou-se determinar os períodos de interferência da mucuna-preta na soqueira cana-de-açúcar, cultivar 'RB855536', e o potencial de redução na produtividade da cultura e na qualidade do produto colhido. Foi utilizado o delineamento experimental em blocos casualizados, com quatro repetições por tratamento, aplicando-se 18 tratamentos divididos em dois grupos. No primeiro, a cultura permaneceu livre da interferência da mucuna-preta desde a brotação até nove épocas do seu ciclo de vida: 0-15, 0-30, 0-45, 0-60, 0-90, 0-120, 0-150, 0-180 dias após a brotação (DAB), 0-colheita. No segundo grupo, a cultura permaneceu em convivência com a mucuna-preta desde a brotação até os mesmos períodos descritos anteriormente. O período crítico de prevenção à interferência da mucuna-preta na soqueira da cultura da cana-de-açúcar ´RB 855536´ abrangeu 138 dias do ciclo da cultura, de 50 DAB (PAI) a 188 DAB (PTPI). E a redução da produtividade da cana-de-açúcar em decorrência da interferência da mucuna-preta foi de 50%, afetando negativamente a qualidade do produto colhido.(AU)

Interference periods of velvet bean in sugarcane / Períodos de interferência de mucuna-preta na cultura da cana-de-açúcar

ABSTRACT: The objective of the present study was to determine the periods of interference of velvet bean on ratoons of sugarcane cultivar 'RB855536' and to identify its potential for decreasing the crop yield and the quality of the harvested product. The experiment was arranged in a randomized block design, with 18 treatments divided into two groups and four replicates per treatment. In the first group, the sugarcane was kept free from velvet bean interference for nine different periods, beginning at bud sprouting: 0-15, 0-30, 0-45, 0-60, 0-90, 0-120, 0-150, and 0-180 days after budding (DAB) and 0-harvest. In the second group, sugarcane was grown in coexistence with velvet bean during the same periods described for the first group. The critical period of interference prevention for velvet bean in ratoons of sugarcane cv. 'RB 855536' lasted 138 days, from 50 DAB (pre-interference period [PIP]) to188 DAB (total period of weed interference prevention [TPIP]). Velvet bean interference caused a 50% decrease in sugarcane yield and negatively affected the quality of the harvested product.

RESUMO: Objetivou-se determinar os períodos de interferência da mucuna-preta na soqueira cana-de-açúcar, cultivar 'RB855536', e o potencial de redução na produtividade da cultura e na qualidade do produto colhido. Foi utilizado o delineamento experimental em blocos casualizados, com quatro repetições por tratamento, aplicando-se 18 tratamentos divididos em dois grupos. No primeiro, a cultura permaneceu livre da interferência da mucuna-preta desde a brotação até nove épocas do seu ciclo de vida: 0-15, 0-30, 0-45, 0-60, 0-90, 0-120, 0-150, 0-180 dias após a brotação (DAB), 0-colheita. No segundo grupo, a cultura permaneceu em convivência com a mucuna-preta desde a brotação até os mesmos períodos descritos anteriormente. O período crítico de prevenção à interferência da mucuna-preta na soqueira da cultura da cana-de-açúcar ´RB 855536´ abrangeu 138 dias do ciclo da cultura, de 50 DAB (PAI) a 188 DAB (PTPI). E a redução da produtividade da cana-de-açúcar em decorrência da interferência da mucuna-preta foi de 50%, afetando negativamente a qualidade do produto colhido.

Interference periods of velvet bean in sugarcane / Períodos de interferência de mucuna-preta na cultura da cana-de-açúcar

The objective of the present study was to determine the periods of interference of velvet bean on ratoons of sugarcane cultivar 'RB855536' and to identify its potential for decreasing the crop yield and the quality of the harvested product. The experiment was arranged in a randomized block design, with 18 treatments divided into two groups and four replicates per treatment. In the first group, the sugarcane was kept free from velvet bean interference for nine different periods, beginning at bud sprouting: 0-15, 0-30, 0-45, 0-60, 0-90, 0-120, 0-150, and 0-180 days after budding (DAB) and 0-harvest. In the second group, sugarcane was grown in coexistence with velvet bean during the same periods described for the first group. The critical period of interference prevention for velvet bean in ratoons of sugarcane cv. 'RB 855536' lasted 138 days, from 50 DAB (pre-interference period [PIP]) to188 DAB (total period of weed interference prevention [TPIP]). Velvet bean interference caused a 50% decrease in sugarcane yield and negatively affected the quality of the harvested product.

Objetivou-se determinar os períodos de interferência da mucuna-preta na soqueira cana-de-açúcar, cultivar 'RB855536', e o potencial de redução na produtividade da cultura e na qualidade do produto colhido. Foi utilizado o delineamento experimental em blocos casualizados, com quatro repetições por tratamento, aplicando-se 18 tratamentos divididos em dois grupos. No primeiro, a cultura permaneceu livre da interferência da mucuna-preta desde a brotação até nove épocas do seu ciclo de vida: 0-15, 0-30, 0-45, 0-60, 0-90, 0-120, 0-150, 0-180 dias após a brotação (DAB), 0-colheita. No segundo grupo, a cultura permaneceu em convivência com a mucuna-preta desde a brotação até os mesmos períodos descritos anteriormente. O período crítico de prevenção à interferência da mucuna-preta na soqueira da cultura da cana-de-açúcar ´RB 855536´ abrangeu 138 dias do ciclo da cultura, de 50 DAB (PAI) a 188 DAB (PTPI). E a redução da produtividade da cana-de-açúcar em decorrência da interferência da mucuna-preta foi de 50%, afetando negativamente a qualidade do produto colhido.