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

Controle do capim-braquiária associado à nutrição com boro no cultivo do mogno-africano em sistema silvipastoril

Dois experimentos foram conduzidos com o objetivo de avaliar o controle do capim-braquiária (Urochloa decumbens) nas linhas de plantio do mogno-africano (Khaya ivorensis) com aplicações de herbicidas isoladas ou combinadas com boro (B), bem como a resposta do mogno-africano a esse micronutriente. Ambos os experimentos foram implantados em delineamento experimental em blocos casualizados em parcelas subdivididas, com quatro repetições. Seis tratamentos foram aplicados nas parcelas: testemunha capinada; testemunha sem capina; glyphosate (1.080 g e.a. ha-1) + chlorimuron-ethyl (10 g i.a. ha-1) + 0,05% v/v de óleo mineral, glyphosate (1.080 g e.a. ha-1) + imazethapyr (100 g i.a. ha-1), glyphosate (1.080 g e.a. ha-1) e oxyfluorfen (480 g i.a. ha-1). As subparcelas foram constituídas pela ausência ou presença de 4 kg de ácido bórico (17% B) para 100 L de água. A associação do ácido bórico aos herbicidas glyphosate mais chlorimuron-ethyl, glyphosate mais imazethapyr, glyphosate ou oxyfluorfen não interfere no controle do capim-braquiária. A adição do ácido bórico à calda dos herbicidas proporciona incrementos nos teores de boro no solo e, consequentemente, aumento nos teores de boro nas folhas do mogno-africano

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

Dinâmica da população de Cardiospermum halicacabum e competição com a cultura da soja

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.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)

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