Effect of different herbicides on Bidens pilosa and Euphorbia heterophylla biotypes resistant to ALS inhibitors

Select herbicides with different mechanism of action is a satisfactory option for resistant weed control. Then, the present work aimed to study the efficiency of different herbicides and their mixtures on Bidens pilosa (blackjack) and Euphorbia heterophylla (wild poinsettia) biotypes, resistant to ALS herbicides in two development stages. The trials we arranged in a completely randomized design with four replications. The treatments tested were (g a.i/a.e ha-1): imazethapyr at 70 and 140 (WG formulation) + 1.0% Assist; imazethapyr at 57.6 and 72 (SL formulation) + 1.0% Assist; imazapic + imazethapyr at 56 and 70 + 1.0% Assist; glyphosate + imazethapyr (596); saflufenacil + glyphosate at 35 + 720 + 0.5% Dash in tank mix, glyphosate at 720 and, a control without herbicide application. Control efficiency was evaluated, as well as dry matter accumulation at the end of the studies. Plants of both species were more susceptible to herbicides at the early stage of development (2 to 4 leaves). The treatments with saflufenacil + glyphosate, (imazethapyr + glyphosate) and glyphosate promoted the best controls, regardless of the species studied and the application stage. The mixture with saflufenacil provided the highest control speed, and the mixture (imazethapyr + glyphosate) was less efficient among three excellent treatments when applied to plants in the 4-6 leaf stage. The treatments (imazethapyr, in both formulations) and (imazethapyr + imazapic) were ineffective in controlling the studied biotypes, regardless of dose and developmental stage studied.

Deposition of diquat with different spray tips, efficiency on common water hyacinth, and effect on water quality

Eichhornia crassipes, known as common water hyacinth, has a high growth rate and produces large amounts of biomass when there are imbalances in water bodies, making it one of the worst aquatic weeds in the world. A study was carried out under small water reservoir field conditions to evaluate the herbicide diquat (960 g ha−1) in controlling this species, at the adult stage development. Four spray tips (AI 11002VS, XR 11002VS and, TXVK-8 with spray volume of 200 L ha−1 and XR 11003VS with 400 L ha−1) were tested. Spraying was performed using a CO2-pressurized sprayer under constant pressure attached to a boat. Plant control was visually evaluated at 1, 3, 7, 11, 14, 21, 29, 60, 87, and 98 days after herbicide application and dry matter accumulation was determined at the end of the experimental period, as well as the spray solution deposition in the application area and water physical and chemical quality. The herbicide diquat was efficient in controlling E. crassipes plants at the dose applied and in development stage of the studied plants, regardless of the type of spray tip at the end of the evaluations. At the beginning of evaluations, the spray tip XR 11002VS was the least effectivity in controlling water hyacinth plants. Spray solution losses were high in all tips tested for control of E. crassipes plants, and the spray tips AI 11002VS and XR 11003VS provided the lowest losses during spraying. No water physical or chemical characteristics were negatively affected by diquat application.

Sowing depth and light intensity in the emergence and development of monocotyledonous weeds

This study aimed to evaluate the effects of different sowing depths and light intensities on the emergence and development of the monocot weed species, Urochloa decumbens and Cenchrus echinatus, under field conditions. Each species constituted an experiment, and the experimental design was completely randomized with four replicates. The treatments were arranged in a 6 x 4 factorial scheme, with six sowing depths (0.5, 1.0, 2.0, 4.0, 8.0, and 12.0 cm) associated with four solar radiation intensities (100%, 70%, 50%, and 30%) obtained through the use of shading screens. Seedling emergence capacity was evaluated daily to obtain the emergence percentage and speed index. Plant height, floral induction time, and plant dry matter at flowering were measured. Even when subjected to different solar radiation intensities, U. decumbens and C. echinatus seedlings emerged at all the sowing depths. Sowing between 2.0- and 4.0-cm depths favored the emergence of seedlings of U. decumbens and C. echinatus. However, sowing at 12-cm depth reduced the emergence of both species regardless of the solar radiation intensity. Urichloa decumbens plants grown under conditions of greater shading showed the lowest values of height and dry matter accumulation during flowering. High levels of shading facilitated only the etiolation of C. echinatus plants. Increased shading flowering time in both species compared to full sunlight.

Selectivity of herbicides applied to Brazilian tree species at post-emergence

The presence of weeds in silvicultural systems has been considered one of the main obstacles to the success of projects designed to recover degraded areas. The aim of this study was to evaluate the selectivity of herbicides applied at post-emergence in the initial growth of seedlings of capixingui (Croton floribundus), açoita-cavalo (Luehea divaricata), and guaritá (Astronium graveolens), in the municipalities of Jaboticabal and Junqueirópolis, state of São Paulo. The experimental design was completely randomized, with four replications, and the treatments consisted of herbicides (g a.i.·ha-1) clethodim + phenoxaprop-p-ethyl (50 + 50), sethoxydim (184), quizalofop-p-ethyl (75), nicosulfuron (50), fluazifop-p-butyl (125), fomesafen (225), haloxyfop-methyl (48), bentazon (720), chlorimuron-ethyl (15), in addition to control without herbicide. The characteristics analyzed were: plant height increase and visual phytointoxication at 7, 14, 21, 28, 35, and 42 days after herbicide application. At the end of the experiment, the shoots of the plants were removed to assess shoot dry matter. The herbicides clethodim + fenoxaprop-p-ethyl, fluazifop-p-butyl, and quizalofop-p-ethyl showed selective potential for the species capixingui, açoita-cavalo, and guaritá. The herbicide chlorimuron-ethyl caused mild intoxication symptoms when applied to seedlings of capixingui and açoita-cavalo; also, it was not selective for the guaritá species grown in Jaboticabal. All species showed selectivity to the herbicides sethoxydim, fomesafen, haloxyfop-methyl, and nicosulfuron, as their growth and initial development were not influenced. The herbicide bentazon caused high percentages of injury to açoita-cavalo plants in both cultivation places, but it did not influence the growth and development of the species.

Use of the imazapic herbicide applied alone or tank mix with imazapyr as growth regulator of lawns

Successive mowing are the major maintenance costs of lawns. Thus, both the expenditure with mowing and the visual and physiological aspect of the lawn have led to the search for alternatives to mechanical management. Thus, this work aimed to study the effects of different rates of imazapic herbicide applied alone or combined with imazapyr as a growth regulator of Bahiagrass (Paspalum notatum) and St. Augustine grass (Stenotaphrum secundatum). The experimental design was a randomized block with four replicates, and the treatments consisted of six rates of imazapic herbicide (35; 70; 105; 140; 175 and 210 g a.i. ha-1) for both species, three rates of imazapic + imazapyr in tank mix (15.57 + 5.25; 23.625 + 7.875; 32.5 + 10.5 g a.i. ha-1) for Bahiagrass and four rates of imazapic + imazapyr mixture (7.875 + 2.625; 15.57 + 5.25; 23.625 + 7.875; 32.5 + 10.5 g a.i. ha-1) for St. Augustine grass. The effect of the treatments was evaluated by observing visible injury symptoms, canopy height, height and number of inflorescences and total dry matter of clippings. Applications of imazapic alone or combined with imazapyr were effective in reducing plant height, number and height of inflorescences and total amount of dry matter of clippings produced by Bahiagrass plants. Imazapic provided satisfactory control of St. Augustine growth, but its utilization caused an increase in the number of inflorescences present in the lawns.

Potential of methane and carbon dioxide in vitro production by Urochloa hybrid subjected to periods of coexistence with weeds / Potencial de produção in vitro de metano e dióxido de carbono por híbrido Urochloa submetido a períodos de coexistência com plantas daninhas

The increased world population has raised the demand for animal proteins, forcing livestock to become productive, efficient, and environmentally sustainable. This study aimed to assess the effect of weed coexistence on productivity, nutritional quality, and potential production of greenhouse gases (GHG) by Convert HD364 grass (Urochloa hibrida cv. Mulato II) under pasture renovation conditions. The experiment was carried out in a randomized block design with four replications and treatments consisting of eight coexistence periods: 0, 15, 30, 45, 60, 75, 90, and 120 days after seedling emergence. Phytosociological assessments were performed in the weed community at the end of each coexistence period. The Convert HD364 grass was assessed for the morphological and chemical-bromatological parameters and for the GHG emission potential. Productivity, nutritional quality, and energy value of the Convert HD364 grass decreased proportionally with the increased period of weed coexistence. The non-coexistence with weeds results in a better in vitro digestibility of organic matter and, consequently, decreases the potential of GHG emission by the dry matter of the Convert HD364 grass.

O aumento da população mundial tem elevado a demanda por proteínas de origem animal, obrigando a pecuária a tornar-se produtiva, eficaz e ao mesmo tempo sustentável. O objetivo deste estudo foi avaliar o efeito da convivência de plantas daninhas sobre a produtividade, qualidade nutricional e potencial de produção de gases de efeito estufa (GEE) pelo capim Convert HD364 (Urochloa hibrida cv. Mulato II) em condição de renovação de pastagem. O experimento foi instalado no delineamento experimental em blocos casualizados, com quatro repetições e os tratamentos constituídos por oito períodos de convivência: 0, 15, 30, 45, 60, 75, 90 e 120 dias após a emergência das plântulas. Avaliações fitossociológicas foram realizadas na comunidade infestante ao final de cada período de convivência. O capim Convert HD364 foi avaliado quanto aos parâmetros morfológicos, químico-bromatológicos e quanto ao potencial de emissão de GEE. Verificou-se que a produtividade, a qualidade nutricional e o valor energético do capim Convert HD364 diminui proporcionalmente ao aumento do período de convivência com as plantas daninhas. A não convivência com plantas daninhas condiciona melhor digestibilidade in vitro da matéria orgânica e, consequentemente, diminui o potencial de emissão de GEE pela matéria seca do capim Convert HD364.

Effects of plant regulators on the growth and flowering of Saint Augustine grass plants / Efeito de inibidores vegetais sobre o crescimento e o florescimento da grama-santo-agostinho

The objective of this work was to evaluate the effects of three plant growth inhibitors on the development and emission of floral rachis of Saint Augustine grass [Stenotaphrum secundatum (Walt.) Kuntzel] plants. The study was carried out in a 15 month old lawn with the experimental plots being distributed in accordance with a complete randomized block design with four replications. The treatments consisted of sole application of trinexapac-ethyl (113, 226, 452, 678, and 904 g ai ha-1), prohexadione-calcium (100 and 200 g ai ha-1), and bispyribac-sodium (40 and 60 g ai ha-1) plus a check treatment in which the plants were not submitted to any of the plant growth inhibitors. The effects of those products were evaluated in terms of visual signs of plant intoxication, plant height, emission and height of floral rachises, and chip total dry matter production. All the plant growth inhibitors resulted in visible injury to the plants but these intoxication signs practically disappeared 28 days after the application. Trinexapac-ethyl at the dose of 904 g ai ha-1 reduced plant height by 59.7%, the emission of floral rachis by 96.4%, and the amount of chip dry matter production by 87.7%. Plant growth inhibitors may reduce the number of times of lawn plants cutting up to 119 days after their application with no harmful effects on the plants visual aspect.

Este trabalho teve o propósito de avaliar o efeito da aplicação de três inibidores de desenvolvimento vegetal sobre o crescimento e a emissão de hastes florais da grama-santo-agostinho [Stenotaphrum secundatum (Walt.) Kuntze]. O estudo foi instalado em um gramado com 15 meses de idade, no delineamento de blocos casualizados, com quatro repetições e os tratamentos compostos por aplicação única de trinexapac-ethyl (113, 226, 452, 678 e 904 g ia ha-1), prohexadione-calcium (100 e 200 g ia ha-1) e bispyribac-sodium (40 e 60 g ia ha-1), além de uma testemunha sem aplicação de inibidor de crescimento. O efeito dos tratamentos foi avaliado quanto à fitointoxicação, por meio de avaliação visual, altura de plantas, altura e emissão de hastes florais e produção total de massa seca de aparas. Todos os inibidores de desenvolvimento vegetal proporcionaram injúrias visíveis sobre a grama-santo-agostinho, mas todos os sintomas de intoxicação praticamente regrediram aos 28 dias após a aplicação. O trinexapac-ethyl aplicado na dose de 904 g ia ha-1 proporcionou redução de 59,7% na altura da grama, de 96,4% e 87,7% na emissão de hastes florais e na quantidade total de massa seca de aparas produzidas pela grama, respectivamente. Gramados formados com grama-santo-agostinho podem ser manejados com a aplicação de inibidor vegetal, com a redução da necessidade de cortes por um período de até 119 dias após a aplicação, sem efeitos severos sobre o aspecto visual sobre o gramado.

Avaliação de pontas e taxas de aplicação na deposição de calda no milho e em plantas daninhas / Influence of nozzle type and spray rates on corn and weed plants drop depositions

O objetivo deste trabalho foi avaliar diferentes pontas e taxas de pulverização na deposição de calda na cultura do milho e nas plantas daninhas Euphorbia heterophylla e Brachiaria plantaginea, localizadas nas linhas e nas entrelinhas da cultura. O experimento foi conduzido em delineamento de blocos ao acaso, em esquema fatorial 2 x 2 (2 pontas de pulverização DG 11002 VS (jato plano e gotas médias) e TXVK08 (jato cônico e gotas muito finas) x 2 taxas de aplicação, 100 e 200 L ha-1) com quatro repetições. As aplicações ocorreram aos 13 dias após a germinação do milho (3 a 5 folhas expandidas), as plantas de E. heterophylla apresentavam de 2 a 4 folhas e as plantas de B. plantaginea de 2 a 3 folhas. Utilizou-se como marcador o corante Azul Brilhante (FD&C-1) na concentração de 3000 ppm. Conclui-se que os maiores depósitos médios nas plantas de milho foram proporcionados pela ponta TXVK08, independente da taxa utilizada e que os depósitos mais uniformes ocorreram quando utilizou-se a taxa de 200 L ha-1. Para as plantas daninhas localizadas na linha da cultura, as pontas de pulverização promoveram depósitos de calda mais uniformes na B. plantaginea do que na E. heterophylla, em ambas as taxas de aplicação. Para a B. plantaginea localizadas na entrelinha da cultura a ponta DG 11002VS foi a que proporcionou depósitos de gotas mais uniformes, sendo que para E. heterophylla a ponta mais eficiente em depositar gotas foi a TXVK08.

The objective of this study was to evaluate different nozzles and spray rates on drop deposition in corn (Zea mays), Euphorbia heterophylla and Brachiaria plantaginea, both weeds located at and between crop rows. The experimental design established was complete random blocks with treatments arranged at 2 x 2 factorial scheme (2 nozzles types: DG11002VS flat flan and medium droplets, TXVK08 cone and very fine droplets; and 2 rates: 100 and 200 L ha-1) with four replications. The spray applications occurred at 13 days after corn germination (3-5 expanded leaves), when E. heterophylla and B. plantaginea plants had 2-4 and 2-3 leaves, respectively. Solution of Brilliant Blue (FD&C-1) dye at 3,000 ppm was used as spray tracer. It was concluded that the greatest average deposits in corn plants was provided by TXVK08, independently of the spray rates used. The most uniform deposits occurred when the spray rates of 200 L ha-1 was used. Spray deposits were most uniform in B. plantaginea compared to E. heterophylla when both weds were located at crop row, independently of nozzle or spray rates. However, the DG 11002VS spray nozzle provided the most uniform drop deposition on B. plantaginea located between the rows, while the most efficient deposition over E. heterophylla located between rows was TXVK08.