Bidens pilosa L. (Asteraceae) control in sunflower with residual herbicides

One of the most damaging species in sunflower crops in Brazil is the hairy beggartick (Bidens pilosa L). The large number of seeds, the various vegetative cycles during the year, the staggered germination and the scarcity of selective and effective herbicides to control this weed in sunflower are some of attributes that hinder the control of hairy beggartick populations. Two experiments were carried out to evaluate the control of hairy beggarticks, as well as sunflower tolerance to herbicides. The treatments were as follows: S-metolachlor (1,200 and 2,400 g ai ha-1), flumioxazin (60 and 120 g ai ha-1), and sulfentrazone (150 and 300 g ai ha-1) and two controls (weedy and weed-free check). The selectivity of the herbicides was higher at low doses. Flumioxazin and sulfentrazone caused injury to sunflowers at the highest doses and mainly in sandy soils. Although S-metolachlor did not cause visual symptoms of injury, the higher dose reduced sunflower yield. The herbicides sulfentrazone and flumioxazin provided satisfactory control of hairy beggartick plants in both types of soils. S-metolachlor presented medium control of hairy beggarticks in clay soil; however, its efficiency was slightly higher when applied in sandy soil. The most efficient herbicide for controlling hairy beggartick plants was flumioxazin, followed by sulfentrazone.One of the most damaging species in sunflower crops in Brazil is the hairy beggartick (Bidens pilosa L). The large number of seeds, the various vegetative cycles during the year, the staggered germination and the scarcity of selective and effective herbicides to control this weed in sunflower are some of attributes that hinder the control of hairy beggartick populations. Two experiments were carried out to evaluate the control of hairy beggarticks, as well as sunflower tolerance to herbicides. The treatments were as follows: S-metolachlor (1,200 and 2,400 g ai ha-1), flumioxazin (60 and 120 g ai ha-1), and sulfentrazone (150 and 300 g ai ha-1) and two controls (weedy and weed-free check). The selectivity of the herbicides was higher at low doses. Flumioxazin and sulfentrazone caused injury to sunflowers at the highest doses and mainly in sandy soils. Although S-metolachlor did not cause visual symptoms of injury, the higher dose reduced sunflower yield. The herbicides sulfentrazone and flumioxazin provided satisfactory control of hairy beggartick plants in both types of soils. S-metolachlor presented medium control of hairy beggarticks in clay soil; however, its efficiency was slightly higher when applied in sandy soil. The most efficient herbicide for controlling hairy beggartick plants was flumioxazin, followed by sulfentrazone

Bidens pilosa L. (Asteraceae) control in sunflower with residual herbicides

One of the most damaging species in sunflower crops in Brazil is the hairy beggartick (Bidens pilosa L). The large number of seeds, the various vegetative cycles during the year, the staggered germination and the scarcity of selective and effective herbicides to control this weed in sunflower are some of attributes that hinder the control of hairy beggartick populations. Two experiments were carried out to evaluate the control of hairy beggarticks, as well as sunflower tolerance to herbicides. The treatments were as follows: S-metolachlor (1,200 and 2,400 g ai ha-1), flumioxazin (60 and 120 g ai ha-1), and sulfentrazone (150 and 300 g ai ha-1) and two controls (weedy and weed-free check). The selectivity of the herbicides was higher at low doses. Flumioxazin and sulfentrazone caused injury to sunflowers at the highest doses and mainly in sandy soils. Although S-metolachlor did not cause visual symptoms of injury, the higher dose reduced sunflower yield. The herbicides sulfentrazone and flumioxazin provided satisfactory control of hairy beggartick plants in both types of soils. S-metolachlor presented medium control of hairy beggarticks in clay soil; however, its efficiency was slightly higher when applied in sandy soil. The most efficient herbicide for controlling hairy beggartick plants was flumioxazin, followed by sulfentrazone

Control of volunteer soybean plants in sunflower crop

Sunflower (Helianthus annuus) sown offseason, after soybean crop (Glycine max), is affected by the competition imposed by volunteer plants. Two experiments were carried out to evaluate the control of volunteer soybean plants in sunflower crops. The sulfentrazone herbicide (75 g ha-1, 100 g ha-1 and 250 g ha-1) causes phytotoxicity to sunflower immediately after application, however, plants recover, with no yield losses. These doses do not cause the total death of volunteer soybean plants, but temporarily paralyzes their growth, avoiding the competition with the sunflower crop. The glufosinate ammonium and ametryn herbicides are effective in controlling volunteer soybean plants, however, symptoms of phytotoxicity in the sunflower crop are high, reflecting in losses of dry weight biomass and crop yield. The other treatments do not provide satisfactory control of volunteer soybean plants and even reduce the sunflower dry weight biomass and yield

Sunflower resistance to acetolactate synthase-inhibiting herbicides

Sunflower is very sensitive to herbicides applied in post-emergence to control broad-leaf weeds. Researchers have developed herbicide-resistant genotypes to imidazolinone herbicides. This study aimed to evaluate the selectivity of imidazolinone and sulfonylurea herbicides applied on sunflower plants (Tera 8003 and Tera 8011) resistant to acetolactate synthase-inhibiting herbicides. The experiments were conducted at Embrapa Gado de Leite, in Coronel Pacheco, Minas Gerais State, and Valença, Rio de Janeiro State, Brazil. The experimental design was randomized complete blocks, with four replications. The treatments consisted of hoed control, imazapyr 25 g a.i. ha-1 and 50 g a.i. ha-1, imazethapyr 70 g a.i. ha-1 and 100 g a.i. ha-1, nicosulfuron 20 g a.i. ha-1 and 32 g a.i. ha-1, and chlorimuron 7.5 g a.i. ha-1 + 0.05% v/v of mineral oil. The crop injury percentage, chlorophyll content (SPAD index), plant height, dry matter production and percentage, and yield were evaluated. The imazethapyr doses (70 g a.i. ha-1 and 100 g a.i. ha-1) were the most selective ones, the nicosulfuron dose (20 g a.i. ha-1) showed moderate tolerance, and imazapyr and chlorimuron caused greater injury, for both sunflower hybrids

Controle de plantas daninhas em cultivos orgânicos de soja por meio de descarga elétrica

Dois experimentos foram instalados em semeadura direta, em área de cultivo orgânico de soja, no município de São Miguel do Iguaçu, Paraná (PR), com o objetivo de avaliar o controle de plantas daninhas na cultura da soja (BRS 232) por meio de descarga elétrica. O delineamento experimental foi blocos casualizados, com quatro repetições. No experimento 1, fixou-se a voltagem de 4400V e,no experimento 2, de 6800V. Em ambos os experimentos,os tratamentos consistiram das variações de rotação do motor do trator (i) 2200rpm (rotações por minutos); (ii) 2000rpm;(iii)1600rpm e as testemunhas(iv) capinada e (v) sem capina. O equipamento utilizado para aplicação dos tratamentos foi o Eletroherb (Sayyou do Brasil). As plantas daninhas existentes na área experimental foram o amendoim-bravo (Euphorbia heterophylla), a corda de-viola (Ipomoea spp.), a guanxuma (Sida spp.), o capim-marmelada(Brachiaria plantaginea) e o capim-colchão (Digitaria spp.). O emprego de descarga elétrica é eficiente no controle das plantas daninhas da cultura da soja. A rotação 2200rpm proporcionou o melhor controle e, consequentemente, a maior produtividade da soja

Tolerance of Khaya ivorensis and Toona ciliata to herbicides

AbstractWe conducted two experiments to evaluate the plant tolerance of African mahogany (Khaya ivorensis) and Australian cedar (Toona ciliata var. australis) to herbicides. The experimental arrangement was a completely randomized design, with four replications. The treatments were as follows: i) untreated control, ii) imazapyr (25 g ai ha-1), iii) oxyfluorfen (360 g ai ha-1), iv) oxyfluorfen (720 g ai ha-1), v) isoxaflutole (75g ai ha-1), vi) isoxaflutole (112.5 g ai ha-1), vii) chlorimuron-ethyl (7.5 g ai ha-1) + 0.05% v / v mineral oil, viii) chlorimuron-ethyl (12.5 g ai ha-1) + 0.05% v / v mineral oil, ix) imazethapyr (100 g ai ha-1), and x) nicosulfuron (40 g ai ha-1). For the African mahogany, imazapyr (25 g ai ha-1), oxyfluorfen (360 g ai ha-1) and chlorimuron-ethyl (7.5 and 12.5 g ai ha-1), showed mild symptoms of phytotoxicity. The oxyfluorfen (720 g ai ha-1), imazethapyr and nicosulfuron were moderately phytotoxics, and isoxaflutole (75 and 112.5 g ai ha-1) was the most phytotoxic herbicide. For Australian cedar, imazapyr (25 g ai ha-1) caused low levels of injury. Oxyfluorfen, isoxaflutole, chlorimuron-ethyl, imazethapyr and nicosulfuron were the most phytotoxic herbicides.Keywords: African mahogany; Australian cedar; weeds; selectivity.Dois experimentos foram conduzidos com o objetivo de avaliar a tolerância de plantas mogno-africano (Khaya ivorensis) e cedro-australiano (Toona ciliata var. australis) a herbicidas. O delineamento experimental foi inteiramente casualizado, com quatro repetições. Tratamentos: i) testemunha sem aplicação, ii) imazapyr (25 g i.a. ha-1), iii) oxyfluorfen (360 g i.a. ha-1), iv) oxyfluorfen (720 g i.a. ha-1), v) isoxaflutole (75 g i.a. ha-1), vi) isoxaflutole (112,5 g i.a. ha-1), vii) chlorimuron-ethyl (7,5 g i.a. ha-1) + 0,05% v/v de óleo mineral, viii) chlorimuron-ethyl (12,5 g i.a. ha-1) + 0,05% v/v de óleo mineral, ix) imazethapyr (100 g i.a. ha-1) e x) nicosulfuron (40 g i.a. ha-1). Para o mogno africano, os herbicidas imazapyr (25 g i.a. ha-1), oxyfluorfen (360 g i.a. ha-1) e chlorimuron-ethyl (7,5 e 12,5 g i.a. ha-1) proporcionaram sintomas leves de fitotoxicidade. O oxyfluorfen (720 g i.a. ha-1), o imazethapyr e o nicosulfuron foram moderadamente fitotóxicos e o isoxaflutole (75 e 112,5 g i.a. ha-1) foi o herbicida mais fitotóxico. Para o cedro australiano, o herbicida imazapyr (25 g i.a. ha-1) proporcionou os menores níveis de injúria. O oxyfluorfen, o isoxaflutole, o chlorimuron-ethyl, o imazethapyr e o nicosulfuron proporcionaram altos níveis de fitotoxicidade.Palavras-chave: Mogno africano; cedro australiano; plantas daninhas; seletividade. AbstractTolerance of Khaya ivorensis and Toona ciliata to herbicides. We conducted two experiments to evaluate the plant tolerance of African mahogany (Khaya ivorensis) and Australian cedar (Toona ciliata var. australis) to herbicides. The experimental arrangement was a completely randomized design, with four replications. The treatments were as follows: i) untreated control, ii) imazapyr (25 g ai ha-1), iii) oxyfluorfen (360 g ai ha-1), iv) oxyfluorfen (720 g ai ha-1), v) isoxaflutole (75g ai ha-1), vi) isoxaflutole (112.5 g ai ha-1), vii) chlorimuron-ethyl (7.5 g ai ha-1) + 0.05% v / v mineral oil, viii) chlorimuron-ethyl (12.5 g ai ha-1) + 0.05% v / v mineral oil, ix) imazethapyr (100 g ai ha-1), and x) nicosulfuron (40 g ai ha-1). For the African mahogany, imazapyr (25 g ai ha-1), oxyfluorfen (360 g ai ha-1) and chlorimuron-ethyl (7.5 and 12.5 g ai ha-1), showed mild symptoms of phytotoxicity. The oxyfluorfen (720 g ai ha-1), imazethapyr and nicosulfuron were moderately phytotoxics, and isoxaflutole (75 and 112.5 g ai ha-1) was the most phytotoxic herbicide. For Australian cedar, imazapyr (25 g ai ha-1) caused low levels of injury. Oxyfluorfen, isoxaflutole, chlorimuron-ethyl, imazethapyr and nicosulfuron were the most phytotoxic herbicides. Keywords: African mahogany; Australian cedar; weeds; selectivity

Recuperación del pasto Cynodon nlemfuensis posterior a desecación con glifosato en pre-siembra de maíz

The aim of this study was to assess the recovery capacity of the African-star-grass (Cynodon nlemfuensis) desiccated with glyphosate in pre-sowing of maize crop. The experimental design was a completely randomized block, with four repetitions. In experiment 1 were applied doses of the equivalent acid (e.a.) of glyphosate herbicide: 0; 720; 1.440; 2.160; 2.880 e 3.600 g ha-1. In experiment 2, was done the no till of the maize, after application of the same doses of glyphosate on African-star-grass and on a hoed control. African-star-grass usually is tolerant to normally recommended doses of the glyphosate herbicide (720 - 2,160 g ha-1). Doses ranging from 1.206 to 1.492 g ha-1 results on suppression of the African-star-grass, avoiding its competition with the maize crop and allowing the recovery of pasture.O objetivo deste trabalho foi avaliar a capacidade de recuperação da grama-estrela-africana (Cynodon nlemfuensis) dessecada com glifosato em pré-semeadura da cultura do milho. O delineamento experimental foi em blocos casualizados, com quatro repetições. No experimento 1, foram aplicadas as doses do equivalente ácido (e.a.) do herbicida glifosato: 0, 720, 1.440, 2.160, 2.880 e 3.600 g ha-1. No experimento 2, foi realizada a semeadura direta do milho após a aplicação das mesmas doses de glifosato sobre a grama-estrela-africana e uma testemunha capinada. A grama-estrela-africana é tolerante a doses normalmente recomendadas do herbicida glifosato (720 a 2160 g e.a. ha-1). Doses de glifosato de 1206 a 1492 g e.a. ha-1 resultam na supressão da grama-estrela-africana, evitando sua competição com a cultura do milho e permitindo a recuperação da pastagem.El objetivo de este estudio fue evaluar la capacidad de recuperación de pasto estrella africana (Cynodon nlemfuensis) desecado con glifosato antes de la siembra del maíz. El diseño experimental fue de bloques al azar con cuatro repeticiones. En el experimento 1 se aplicaron las dosis del equivalente ácido (e.a.) del herbicida glifosato: 0 , 720, 1440 , 2160 , 2880 y 3600 g ha-1. En el experimento 2 se realizó la siembra directa de maíz después de la aplicación de las mismas dosis de glifosato en el pasto estrella africana y un control realizado manualmente con azada. El pasto estrella africana es tolerante a dosis habitualmente recomendadas del herbicida glifosato (720-2160 g e.a. ha-1). Dosis de glifosato de 1206-1492 g e.a. ha-1 dieron como resultado la supresión del pasto estrella africana, evitando la competencia con el maíz y permitiendo la recuperación de las pasturas

Population dynamics of Cardiospermum halicacabum and competition with soybeans

O balãozinho (Cardiospermum halicacabum), planta daninha introduzida recentemente no Paraná, tem causado perdas econômicas em lavouras de soja no Sul do Brasil. O objetivo deste trabalho foi determinar época e taxa de emergência, competição e sobrevivência de balãozinho na cultura da soja cultivar Embrapa 62, em dois sistemas de manejo. O experimento foi instalado em Londrina, PR, em maio de 1997, e conduzido por três anos consecutivos. Cinco densidades de semeadura de balãozinho (0, 60, 120, 240 e 480 sementes/m2) foram estabelecidas na cultura da soja sob semeadura convencional e direta. O delineamento experimental foi em blocos casualizados, com parcelas subdivididas e quatro repetições. A redução média anual do banco de sementes foi de 61,6% e 56,4%, em relação às semeaduras convencional e direta, correspondendo às sobrevivências de seis e sete anos, respectivamente. Taxas anuais de emergência, na ausência de reinfestações, foram maiores em semeadura direta (42,6%, 32,0% e 5,0%) do que na convencional (29,9%, 10,9% e 0,7%), nos três anos. Perdas de produtividade de soja foram estimadas em 8,1% com a presença de 10 plantas/m2 de balãozinho, em 3.549 kg/ha de soja. O balãozinho apresenta significativa capacidade de infestação e competição com a soja, tendendo a ser eliminado por condições ambientais que favoreçam o ataque de míldio (Peronospora farinosa).Balloonvine (Cardiospermum halicacabum) was recently introduced in Paraná State, and it has caused economical damages in soybean crop in the Southern region of Brazil. In order to determine time and emergence rate, the competition and the survival of balloonvine with soybeans cultivar Embrapa 62, grown under two management systems, an experiment was carried out at Londrina, PR, from 1997 to 2000. Five population densities of ballonvine (zero, 60, 120, 240 and 480 seeds/m2) were established by sowing seeds in till and no-till managements for soybeans. A split-plot completely randomized block, with four replications, was used. An annual seedbank decrease rate of 61.6% and 56.4% was observed for till and no-till, respectively, related to six and seven years survival. Annual rates of emergence, in the absence of reinfestations, were higher in no-till (42.6%, 32.0% and 5.0%) than till (29.9%, 10.9% and 0.7%), in those three years. Losses of soybeans were estimated at an average of 8,1% in the presence of 10 plants/m2 of balloonvine over 3,549 kg/ha of soybeans. Balloonvine presents significant infestation and competition hability in the soybean crop, and it tends to be eliminated by environmental conditions that favor downy mildio (Peronospora farinosa) attach

Aluminum toxicity tolerance in elephant grass

El logro de los cultivares de forrajeras mejoradas, tolerantes a la toxicidad de aluminio, se considera la mejor alternativa para sortear las dificultades expresadas por extensas áreas de suelos ácidos con altas concentraciones de aluminio, presente en Brasil. Por lo tanto, los objetivos de este estudio fueron: a) evaluar el nivel de aluminio en solución nutritiva y la característica más importante de la discriminación de genotipos de pasto elefante; b) verificar la existencia de variabilidad genética entre algunos accesos de pasto elefante de la Embrapa Ganado ABG lácteos para la tolerancia al aluminio, y c) estudiar la interacción del genotipo con los niveles de aluminio. En invernadero se evaluaron 26 genotipos de pasto elefante y cuatro niveles de aluminio (0, 15, 30 y 45 ppm) en un experimento realizado en un diseño completamente al azar con tres repeticiones en contenedores con una planta. Tomó nota de los datos relativos al peso seco del vástago (SDW), peso seco de raíz (PSR), altura de los brotes (APA) y la longitud de las raíces (CR). Con las medias de los genotipos de aluminio diferentes procedió a un análisis de la adaptabilidad y la estabilidad mediante el metodologías de Eberhart y Russell y Annicchiarico. Se ha encontrado que existe variabilidad entre los genotipos de pasto elefante para la tolerancia a los diferentes niveles de aluminio, teniendo en cuenta las características PSPA, PSR, APA y CR. El nivel de 15 ppm de aluminio se consideró los materiales más adecuados para identificar tolerantes y sensibles a los tóxicos de aluminio. Las características PSPA y APA fueron más adecuados para una nueva evaluación de tolerancia de pasto elefante con el aluminio en solución nutritiva. El genotipo Taiwan121 y Australiano se presentaron adaptable y estable en las dos metodologias utilizados.A obtenção de cultivares forrageiras melhoradas, tolerantes ao alumínio tóxico, é considerada a melhor alternativa para contornar as dificuldades expressas pelas extensas áreas de solos ácidos, com elevada concentração de alumínio, presentes no Brasil. Por isso, os objetivos do presente trabalho foram: a) avaliar o nível de alumínio da solução nutritiva e a característica mais importante para a discriminação de genótipos de capim-elefante; b) verificar a existência de variabilidade genética entre alguns acessos de capim-elefante do BAG da Embrapa Gado de Leite para a tolerância ao alumínio e; c) estudar a interação genótipos por níveis de alumínio. Em casa-de-vegetação foram testados 26 genótipos de capim-elefante e quatro níveis de alumínio (0, 15, 30 e 45 ppm) em experimento conduzido no delineamento inteiramente casualizado, com três repetições e parcelas de um vaso com uma planta. Anotaram-se dados referentes ao peso seco da parte aérea (PSPA), peso seco das raízes (PSR), altura da parte aérea (APA) e o comprimento das raízes (CR). Com as médias dos genótipos nos diferentes níveis de alumínio procedeu-se a uma análise de adaptabilidade e estabilidade utilizando as metodologias de Eberhart e Russell e Annicchiarico. Foi constatada a existência de variabilidade entre os genótipos de capim-elefante para a tolerância aos diferentes níveis de alumínio, considerando-se as características PSPA, PSR, APA e CR. O nível de 15 ppm de alumínio foi considerado o mais adequado para identificar materiais tolerantes e sensíveis à toxidez por alumínio. As características PSPA e APA mostraram-se mais indicadas para futuras avaliações de tolerância de capim-elefante ao alumínio, em solução nutritiva. Os genótipos Taiwan A 121 e Australiano apresentaram-se adaptados e estáveis em relação às duas metodologias empregadas.The use of forages with aluminum tolerance is the best alternative to the wide areas of acid soils with high aluminum concentrations in Brazil. So, the goals of this work were: to evaluate the aluminum level in the nutrient solution and the most important characteristics for elephant grass genotypes discrimination; to verify the existence of genetic variability between accesses of elephant grass of BAG Embrapa Gado de Leite for aluminum tolerance, and; to study the genotypes and aluminum levels interaction. In a greenhouse experiment 26 elephant grass genotypes and four aluminum levels (0, 15, 30 e 45 ppm) were tested, using a randomized design, with three replications and only one plant per vase. Data of dry matter of aerial part (DMAP), root dry matter (RDM) height of aerial part (HAP) and root length (RL) were collected. Using the metodologies of Eberhardt and Russell and Annicchiarico, analysis of adaptability and stability were done using the averages of the genotypes on the different levels of aluminum. There was variability between elephant grass genotypes for tolerance to the different aluminum levels, regarding the characteristics DMAP, RDM, HAP and RL. The level of 15 ppm of aluminum was considered the most appropriated to identify tolerant and sensible genotypes to aluminum toxicity. DMAP and HAP were the characteristics indicated for future evaluations of elephant grass for aluminum tolerance using nutrient solution. Taiwan A 121 and Australiano genotypes presented adaptability and stability in relation to the two employed methodologies

Phytosociological census of weeds in the sunflower crop

O objetivo deste trabalho foi realizar um levantamento das plantas daninhas infestantes na pré-colheita da cultura de girassol em lavouras dos municípios do sudoeste goiano (Chapadão do Céu, Jataí e Montividiu) e em Chapadão do Sul, MS. Foram amostradas, no período de maio a junho de 2002, 51 propriedades dos quatro municípios, totalizando uma área de 583 m2. As espécies daninhas foram identificadas e contadas mediante a aplicação de um quadrado de 1,0x1,0 m, colocado ao acaso dentro da área ocupada pelas lavouras. Foram obtidos os valores de freqüência, densidade, abundância e índice de importância relativa. Plantas voluntárias de soja e de milho fazem parte da flora daninha infestante de lavouras de girassol dessa região. As famílias Poaceae, Asteraceae e Euphorbiaceae são as que apresentam maior número de espécies. As principais plantas daninhas infestantes na região são, em ordem decrescente, Ageratum conyzoides, Chamaesyce hirta, Cenchrus echinatus, Bidens sp., Euphorbia heterophylla e Commelina benghalensis.The objective of this work was to survey the weeds in the preharvest of the sunflower crop in growers field of the southwest regions of Goiás State (Chapadão do Céu, Jataí and Montividiu) and Chapadão do Sul, Mato Grosso do Sul State, Brazil. Fifty one farms were evaluated, during the period of May to June, 2002, in a total of 583 m2 of area. The weeds were identified and counted inside a square (1.0x1.0 m), applied in each area, in order to determine the frequency, density, abundance and relative importance. Volunteer soybean (Glycine max) and corn (Zea mays) are part of the weed species in sunflower crop in the area. The botanical families Poaceae, Asteraceae and Euphorbiaceae present larger number of species. The main weeds found in the area are, in decreasing order, Ageratum conyzoides, Chamaesyce hirta, Cenchrus echinatus, Bidens sp., Euphorbia heterophylla and Commelina benghalensis