This study aimed to assess the phytosociology of weeds as a function of different crop management technology levels in cassava production. Field experiments were conducted in Santa Maria (29°41′03″ ...S; 53°48′25″ W) and Itaqui (lat. 29°07′31″ S; long. 56°33′11″ W), Rio Grande do Sul, Brazil. Treatments consisted of three technology levels: low (postemergence weeding without basal dressing); medium (weeding performed at 7 and 40 days after planting and fertilization with 6.25, 25, and 25 kg⋅ha −1 of N, P, and K, respectively); and high (postemergence application of s-metolachlor; 1250 kg⋅ha −1 of lime and 12.5, 50, and 50 kg⋅ha −1 of N, P, and K, respectively). Weed frequency, density, relative abundance, and importance values were calculated for each location. Then, locations were compared using a dissimilarity matrix. Weed density and diversity decreased linearly as technology levels increased. The predominant weed species found in Itaqui and Santa Maria belong to the Poaceae family. Itaqui presented highest weed diversity among the locations. The genus Cyperus had the highest importance value index in Santa Maria. The use of S-metolachlor at the high technology level provided a lower frequency and lower diversity of weed species than did levels without chemical control in Itaqui and Santa Maria.
Due to the evolution of resistant weeds to glyphosate, the new technologies Xtend® and Enlist® cropping systems are expected to boost the use of auxin herbicides dicamba and 2,4-D. This study ...examined the effects of two formulations of 2,4-D and dicamba in tank-mixtures with other pesticides on selected physico-chemical properties of the spray solution, such as stability and pH, as well as other characteristics, such as size in dropcard and surface tension. The research included two factors, factor A comprised the herbicides dicamba and 2,4-D amine and choline salts and a auxin herbicide-free treatment, while factor B comprised 12 pesticides commonly sprayed in Brazil (i.e., five formulations of glyphosate, clethodim, haloxyfop-p-methyl, trifloxystrobin + prothioconazole, azoxystrobin + benzovindiflupyr, mancozeb, chlorantraniliprole, and thiamethoxam + lambda-cyhalothrin). Stability and pH, surface tension, and droplet parameters of the tank-mixtures were analyzed. No incompatibility was observed in the tank mixtures tested. Mixing dicamba with clethodim and haloxyfop-p-methyl resulted in pH values below 4.5. Auxin herbicides did not show pH buffering capacity and did not prevent pH changes when the others pesticides were added to the tank-mixtures. All mixtures affected surface tension of herbicides relative to the single solutions. The results support the use of auxin herbicides with other pesticides, given that the use of auxin herbicides will probably increase, following the adoption of new dicamba and 2,4-D technologies.
Carrier water quality is one of the main characteristics for an efficient and safe spraying of pesticides. Overall related to the levels of pH and hardness. The objective was to evaluate the ...interaction between water pH and storage time of the spray, containing 2,4-D amine, 2,4-D choline and dicamba, on the visible efficacy in Ipomoea triloba, Bidens pilosa, Amaranthus viridis; and water hardness on I. triloba. Three studies were carried out in a greenhouse. Study 1 with a 3x5 factorial, which factor A being pH of 2, 6 and 10 and factor B being 0, 2, 6, 24 and 36 hours of application after the mixture. Study 2 was a 3x5 factorial for each herbicide, whith factor A being the levels of pH (2, 6 and 10) and factor B being 0, 6, 12, 24 and 48 hours of application after the mixture. The study 3 is a 3x7 factorial, with factor A being the herbicides and factor B levels of water hardness: 0, 65, 125, 250, 500, 750 and 1000 parts per million. The pH of all solutions remained stable for 48 hours after preparation. However, did not interfere in efficacy of dicamba in I. triloba. Also, longer time between preparing the spray with 2,4-D formulations and application caused reduction efficacy on I. triloba. Also, the level of water hardness decreased control on I. triloba. The pH of carrier water did not affect efficacy of 2,4-D and dicamba on the weeds; however, longer time of the spray application reduce the visible efficacy.
RESUMO: A qualidade da água é uma das principais características para uma aplicação eficiente e segura de pesticidas. De maneira geral, a qualidade da água está relacionada aos níveis de pH e dureza. Assim, o objetivo foi avaliar a interação entre o pH da água e tempo de mistura da calda contendo os herbicidas 2,4-D amina, 2,4-D colina e dicamba, na eficácia visível em Ipomoea triloba, Bidens pilosa, Amaranthus viridis; além dos níveis de dureza da água em I. triloba. Três estudos feitos em estufa. Estudo 1 em fatorial 3x5 sendo o fator A pH de 2, 6 e 10 e o fator B 0, 2, 6, 24 e 26 horas da mistura até a aplicação. Estudo 2 em fatorial 3x5 para cada herbicida, sendo o fator A pH de 2, 6 e 10 e o fator B 0, 6, 12, 24 e 48 horas da mistura até a aplicação. Estudo 3 em fatorial 3x7 sendo o fator A os herbicidas e o fator B níveis de dureza da água: 0, 65, 125, 250, 500, 750 e 1000 partes por milhão. O pH manteve-se estável nas 48 horas. Entretanto, não interferiu na eficácia de dicamba em I. triloba. Além disso, maior tempo entre o preparo da calda com as formulações de 2,4-D e a aplicação causou redução da eficácia em I. triloba. Ainda, a dureza da água diminuiu o controle sobre I. triloba. O pH não afetou 2,4-D e dicamba sobre as plantas, entretanto, maior tempo de aplicação reduz a eficácia.
Abstract The objective of this work was to evaluate the selectivity of pre- and post-emergent herbicides and their efficiency in weed control, as well as the growth and quality of floral stems, in a ...gladiolus (Gladiolus x grandiflorus) crop in two growing seasons. The experiments were carried out in the field, where the planted gladiolus received the application of pre- and post-emergent herbicides, with and without mechanical weed control. At 7, 14, 21, and 28 days after emergence (DAE), monocotyledon and eudicotyledon control and phytotoxicity to gladiolus plants were evaluated. At 28 DAE, the shoot dry matter of weeds and gladiolus plants was also evaluated. The s-metolachlor and diuron pre-emergent herbicides and the haloxyfop-p-methyl post-emergent herbicide are selective to gladiolus plants in both seasons, which allows of the production of floral stems with commercial quality. The s-metolachlor and haloxyfop-p-methyl herbicides also promote an efficient control of monocotyledons regardless of the growing season. Although, when applied, saflufenacil and 2,4-D cause phytotoxicity in the vegetative phase of gladiolus, they do not affect the production of floral stems and control satisfactorily eudicotyledons in the second season.
Resumo O objetivo deste trabalho foi avaliar a seletividade de herbicidas pré e pós-emergentes e a sua eficiência no controle de plantas daninhas, bem como o crescimento e a qualidade de hastes florais, na cultura do gladíolo (Gladiolus x grandiflorus), em duas épocas de cultivo. Os experimentos foram conduzidos a campo, onde os gladíolos plantados receberam a aplicação de herbicidas pré e pós-emergentes, com e sem controle mecânico das plantas daninhas. Aos 7, 14, 21 e 28 dias após a emergência (DAE), avaliaram-se o controle de monocotiledôneas e eudicotiledôneas, além da fitotoxicidade no gladíolo. Aos 28 DAE, também foi avaliada a massa seca da parte aérea das plantas daninhas e dos gladíolos. Os herbicidas pré-emergentes s-metolacloro e diuron e o pós-emergente haloxifope-p-metílico são seletivos ao gladíolo, em ambas as épocas de cultivo, o que possibilita a produção de hastes florais com qualidade comercial. Os herbicidas s-metolacloro e haloxifope-p-metílico também promovem controle eficiente de monocotiledôneas independentemente da época de cultivo. Embora, quando aplicados, saflufenacil e 2,4-D causem fitotoxicidade na fase vegetativa do gladíolo, não afetam a produção de hastes florais e controlam satisfatoriamente as eudicotiledôneas no segundo cultivo.
ABSTRACT The drought stress tolerance may differ among species and cultivars. The drought effect on plants depends on the impact on the plant’s physiological, biochemical and molecular processes, as ...well as on its ability to adapt under these conditions. This study aimed to evaluate the physiological and biochemical responses, and determine the expression of the genes OsAPX2, OsHSP24.15, OsHSP71.10 and OsHSP85.88 under drought conditions in rice, weedy rice and barnyardgrass. A greenhouse experiment was performed in a complete randomized design, with four replications and two factors: water conditions (well-watered and water deficit) and plant species rice (Oryza sativa cv. Puitá), weedy rice (Oryza spp.) and barnyardgrass (Echinochloa spp.). Under drought conditions, the rice and weedy rice plants showed more cellular damage than the barnyardgrass, and the three species showed a reduced photosynthetic rate. C3 plants (rice and weedy rice) increased the damage to lipids and proteins at 5 days of drought. However, for C4 plants (barnyardgrass), the drought conditions did not affect the biochemical parameters. The expression of the OsHSP85.88 gene increased in the three plants exposed to water deficit.
RESUMO A tolerância ao estresse hídrico pode diferir entre espécies e cultivares. O efeito da seca nas plantas depende do impacto nos processos fisiológicos, bioquímicos e moleculares da planta e da capacidade de a mesma se adaptar a essas condições. Objetivou-se avaliar as respostas fisiológicas e bioquímicas, bem como determinar a expressão dos genes OsAPX2, OsHSP24.15, OsHSP71.10 e OsHSP85.88 em condições de seca em arroz, arroz daninho e capim-arroz. Foi realizado experimento em casa-de-vegetação, em delineamento inteiramente casualizado, com quatro repetições e dois fatores: condições hídricas (bem irrigado e déficit hídrico) e espécies de plantas arroz (Oryza sativa cv. Puitá), arroz daninho (Oryza spp.) e capim-arroz (Echinochloa spp.). Em condições de seca, as plantas de arroz e arroz daninho apresentaram mais danos celulares do que o capim-arroz, e as três espécies apresentaram taxa fotossintética reduzida. As plantas C3 (arroz e arroz daninho) aumentaram os danos aos lipídios e proteínas aos 5 dias de seca. No entanto, para plantas C4 (capim-arroz), as condições de seca não afetaram os parâmetros bioquímicos. A expressão do gene OsHSP85.88 aumentou nas três plantas expostas ao déficit hídrico.
Efficient herbicide absorption and translocation, and satisfactory weed control can be affected by the site of herbicide application. However, during harvesting of crops of previous soybean sowing, ...the cutting process made by harvesters on the fleabane may generate a difficult management in pre sowing of the crop by limiting the leaf area of the absorption of the herbicide. Experiments were conducted to evaluate the control efficiency and translocation potential of saflufenacil in fleabane plants with different leaf and stem conditions. Experiment I was arranged in a 2x10 factorial scheme, with factor A corresponding to leaf integrity, and factor B corresponding to different levels of injury and saflufenacil application. Weed control was evaluated at 7, 14, and 21 days after herbicide treatment (DAT), and dry matter was evaluated at 21 DAT. Experiment II consisted of applying saflufenacil to different fleabane structures, where the percentage of necrotic area was evaluated at 1, 3, 5, and 7 DAT. Fleabane control was higher than 75% in all treatments with saflufenacil application, with greater control in plants previously defoliated. Saflufenacil application on 10 and 20 cm hairy fleabane plants was also efficient in all treatments. Saflufenacil application in old stem showed a larger necrotic area, while application in the site of the cutting resulted in a lower necrotic area. The main pathway for translocation of saflufenacil is via xylem and the stem proved to be the absorption element of the herbicide when leaf area is limited.
The study of herbicide dynamics in the soil and their interaction with the components of the environment makes it possible to ensure the selectivity of crops and the agronomical efficiency. The aim ...of this research was to evaluate the influence of soil physicochemical properties on the emergence and growth of soybean, with pre-emergence application of various saflufenacil rates. An experiment was carried out in a greenhouse with a completely randomized design, testing different soil types containing “Erechim”, “Santa Maria” and “Eldorado do Sul”, at different saflufenacil rates: 0, 12.5, 25, 50, 100, 200, 400 g a.i. · ha–1. The application was performed 1 day after soybean sowing, and analyzed variables were: the phytotoxicity emergence of seedlings, dry mass and height of the soybean. The saflufenacil effective dose of 50% response in soybean (ED50) and the characteristics of the soils showed that the soil contained clay and sand which were the components most related to the saflufenacil availability to the plants. A lower ED50 by phytotoxicity to the soybean was found in soil with lower and greater content of clay and sand, respectively. The physicochemical properties of soil influenced the saflufenacil activity, having greater potential of injury to soybean in the soil from Eldorado do Sul, due to its clay and sand content.
Synthetic auxin herbicides constitute major alternatives for managing tough-to-kill weeds such as Ipomoea spp. Adjuvant use is known to positively affect the biological efficacy of pesticides by ...modifying key spraying solution and droplet properties. Determining to what extent the use of adjuvants could change spray solution parameters and affect synthetic auxin herbicides’ efficiency for Ipomoea spp. control were the research goals. The study was conducted in two phases: laboratory and field, respectively. In the laboratory, the pH, the surface tension, and the resources of the herbicide drops were measured. In the field, weed control was evaluated. All adjuvants modified spray solution properties, lowering surface tension values. Most adjuvants decreased pH values as well as number and density of droplets due to an increase in droplet size. Regardless of adjuvant usage, Ipomoea spp. control levels rose more rapidly following 2,4-D spraying rather than dicamba, resulting in lower biomass accumulation when the former was used. Dicamba-containing treatments displayed slightly but significantly lower Ipomoea spp. control levels at the end of the evaluation period. Herbicide efficacy for Ipomoea spp. control was not improved upon the addition to the spray solution of any of the tested adjuvants. Adjuvant use altered spraying solution and droplet properties. 2,4-D spraying allowed for lower Ipomoea spp. biomass and greater control levels relative to dicamba, suggesting it might constitute a better option for Ipomoea spp. control. Even though herbicide efficacy was not improved with adjuvants, their use should still be considered given favorable spraying solution alterations, mainly with some alteration in droplet sizes despite the use of similar spray nozzles tips - maintaining weed control efficacy.
Conyza spp. é uma espécie de difícil controle, principalmente quando se encontram com maior estatura e em estádios mais avançados de desenvolvimento. O estudo objetivou avaliar a eficiência de ...controle de 2,4-D colina e da mistura formulada de 2,4-D colina e glifosato em Conyza spp. com diferentes estaturas e estádios de desenvolvimento. Os fatores avaliados foram três estaturas de Conyza spp. (1-2; 10-12 e 25-30 cm); dois herbicidas 2,4-D colina (EC) e 2,4-D colina + glifosato (ED); e doses destes herbicidas correspondentes a 0x, 1/2x, 1x, 2x e 4x a dose recomendada. O herbicida ED proporcionou melhor controle comparativamente ao EC em todas as doses e estaturas avaliadas. O controle de Conyza spp. deve ser realizado em estágios iniciais de desenvolvimento, pois ambos os herbicidas nas doses iguais ou superiores as doses de registro são eficazes para o controle, o que não ocorre em estatura maiores que 10 cm ou estágio de 19 folhas.
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