Normalized difference vegetation index for desiccation evaluation with glyphosate + 2, 4-D in magnetized spray solution / Índice de vegetação por diferença normalizada para avaliação de dessecação com glyphosate + 2, 4-D em calda magnetizada

Water magnetization and geoprocessing are increasingly utilized tools in weed management. Our objective was to study the influence of water magnetization on herbicide efficiency and to verify whether there is a relationship between control scores and the normalized difference vegetation index (NDVI). In the laboratory experiment, water was subjected to magnetization and evaluated with respect to four characteristics. In the field experiment, plots of Brachiaria grass were subjected to treatments in a factorial scheme (6 × 2 + 1). Six herbicidal factors (doses of glyphosate and glyphosate + 2,4-D) and the magnetization or absence of magnetization of the spray solution were evaluated and compared against the control treatment (without spraying). Weed control assessments were carried out six times. Images were obtained using an embedded multispectral camera to determine the NDVI values. Data related to water characteristics were analyzed using the t test. Weed control and NDVI data were subjected to analysis of variance and are presented in regression graphs. Dispersion analysis of NDVI data was performed according to the control scores. The magnetization process decreased the pH of the water and increased the surface tension, but it did not influence the control scores or the NDVI. As the glyphosate dose was increased, the control scores were higher and the NDVI values were lower. Magnetized water did not affect the biological efficiency of the herbicides, and there was a strong correlation between the control scores and the NDVI values.

A magnetização da água e o geoprocessamento são ferramentas cada vez mais utilizadas no manejo de ervas daninhas. Nosso objetivo foi estudar a influência da magnetização da água na eficiência do herbicida e verificar se existe uma relação entre os escores de controle e o índice de vegetação por diferença normalizada (NDVI). No experimento de laboratório, a água foi submetida à magnetização e avaliada em relação a quatro características. No experimento de campo, parcelas de capim-braquiária foram submetidas a tratamentos em esquema fatorial (6 × 2 + 1). Seis fatores herbicidas (doses de glyphosate e glyphosate + 2,4-D) e a magnetização ou ausência de magnetização da calda foram avaliados e comparados com o tratamento controle (sem pulverização). Avaliações de controle de plantas daninhas foram realizadas seis vezes. As imagens foram obtidas usando uma câmera multiespectral incorporada para determinar os valores de NDVI. Os dados relacionados às características da água foram analisados por meio do teste t. O controle de plantas daninhas e os dados de NDVI foram submetidos à análise de variância e são apresentados em gráficos de regressão. A análise de dispersão dos dados NDVI foi realizada de acordo com os escores de controle. O processo de magnetização diminuiu o pH da água e aumentou a tensão superficial, mas não influenciou nos escores de controle ou no NDVI. Conforme a dose de glyphosate foi aumentada, os escores de controle foram maiores e os valores de NDVI foram menores. A água magnetizada não afetou a eficiência biológica dos herbicidas, e houve uma forte correlação entre os escores de controle e os valores de NDVI.

Normalized difference vegetation index for desiccation evaluation with glyphosate + 2, 4-D in magnetized spray solution / Índice de vegetação por diferença normalizada para avaliação de dessecação com glyphosate + 2, 4-D em calda magnetizada

Abstract Water magnetization and geoprocessing are increasingly utilized tools in weed management. Our objective was to study the influence of water magnetization on herbicide efficiency and to verify whether there is a relationship between control scores and the normalized difference vegetation index (NDVI). In the laboratory experiment, water was subjected to magnetization and evaluated with respect to four characteristics. In the field experiment, plots of Brachiaria grass were subjected to treatments in a factorial scheme (6 × 2 + 1). Six herbicidal factors (doses of glyphosate and glyphosate + 2,4-D) and the magnetization or absence of magnetization of the spray solution were evaluated and compared against the control treatment (without spraying). Weed control assessments were carried out six times. Images were obtained using an embedded multispectral camera to determine the NDVI values. Data related to water characteristics were analyzed using the t test. Weed control and NDVI data were subjected to analysis of variance and are presented in regression graphs. Dispersion analysis of NDVI data was performed according to the control scores. The magnetization process decreased the pH of the water and increased the surface tension, but it did not influence the control scores or the NDVI. As the glyphosate dose was increased, the control scores were higher and the NDVI values were lower. Magnetized water did not affect the biological efficiency of the herbicides, and there was a strong correlation between the control scores and the NDVI values.

Resumo A magnetização da água e o geoprocessamento são ferramentas cada vez mais utilizadas no manejo de ervas daninhas. Nosso objetivo foi estudar a influência da magnetização da água na eficiência do herbicida e verificar se existe uma relação entre os escores de controle e o índice de vegetação por diferença normalizada (NDVI). No experimento de laboratório, a água foi submetida à magnetização e avaliada em relação a quatro características. No experimento de campo, parcelas de capim-braquiária foram submetidas a tratamentos em esquema fatorial (6 × 2 + 1). Seis fatores herbicidas (doses de glyphosate e glyphosate + 2,4-D) e a magnetização ou ausência de magnetização da calda foram avaliados e comparados com o tratamento controle (sem pulverização). Avaliações de controle de plantas daninhas foram realizadas seis vezes. As imagens foram obtidas usando uma câmera multiespectral incorporada para determinar os valores de NDVI. Os dados relacionados às características da água foram analisados ​​por meio do teste t. O controle de plantas daninhas e os dados de NDVI foram submetidos à análise de variância e são apresentados em gráficos de regressão. A análise de dispersão dos dados NDVI foi realizada de acordo com os escores de controle. O processo de magnetização diminuiu o pH da água e aumentou a tensão superficial, mas não influenciou nos escores de controle ou no NDVI. Conforme a dose de glyphosate foi aumentada, os escores de controle foram maiores e os valores de NDVI foram menores. A água magnetizada não afetou a eficiência biológica dos herbicidas, e houve uma forte correlação entre os escores de controle e os valores de NDVI.

Allelopathy of Ricinus communis and light spectrum variation decrease emergence and growth of Cyperus rotundus

Weeds negatively influence agricultural production. However, those losses depend on weed specie, its time of emergence, and period of interference on agricultural crops. Synthetic herbicides are commonly used to control these plants species; however, they may cause damage to the environment, human beings and animals health, and this problem justify the need to develop alternative bioherbicides. To evaluate the allelopathic potential of Ricinus communis (Castor bean) and light spectrum variation on the emergence and growth of Cyperus rotundus L., a trial was carried out in a protected environment with 15% of brightness reduction at the Center for Agricultural and Environmental Sciences at the Paraíba State University. Four aqueous extract concentrations of R. communis leaves were tested (0, 5, 10, and 15%) and four light spectrums variations (white, purple, blue, and red lights). Variables such as emergence, length, dry matter accumulation and growth rates of shoots and root of C. rotundus seedlings were assessed. Data were analyzed by normality test, analysis of variance, polynomial regression, and averages test. Soot and root emergence, length, and dry matter accumulation of C. rotundus seedlings were reduced due to the allelopathy caused by R. communis aqueous extract leaves (15% concentration) and under purple or red light spectrum radiation.

Efficacy of the herbicides indaziflam and clomazone on problematic weeds of family poaceae to sugarcane crop

It is believed that indaziflam gives a longer period of weed control compared to clomazone, irrespective of the type or texture of the soil. Thus, the aim of this study was to evaluate pre-emergent control in five problematic weed species of family Poaceae to sugarcane, using the herbicides indaziflam and clomazone in two soils of different textures. Two experiments were carried out, one in a soil of a sandy-loam texture and the other in a clayey soil. For both experiments, a randomised block design of split plots was chosen, with four replications. The treatments consisted of the herbicides indaziflam (75 and 100 g ai ha-1), clomazone (1080 g ai ha-1) and a control with no herbicide. In the subplots, the treatments were Digitaria horizontalis, Panicum maximum, Rottboellia cochinchinensis, Urochloa decumbens and Urochloa plantaginea. Both herbicides were more effective in the clayey soil, but with indaziflam (100 g ai ha-1), more than 90% control of the weeds remained after 240 days after application (DAA), whereas for clomazone, control remained only up to 90 DAA. The herbicide clomazone did not satisfactorily control the weeds in the sandy-loam soil. The herbicide indaziflam did not control U. decumbens in the sandy-loam soil. D. horizontalis and R. cochinchinensis were the most sensitive species to the herbicide indaziflam, irrespective of soil texture.

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.

Herbicide efficacy in the fall management of Richardia brasiliensis, Commelina benghalensis, Conyza sumatrensis AND Digitaria insularis

Other herbicides, alone or in combination with glyphosate, may be effective in controlling Richardia brasiliensis, Commelina benghalensis, Conyza sumatrensis e Digitaria insularis. Therefore, the aim of this study was to evaluate the efficacy of herbicides, alone or in combination, in the control of these weeds in the off-season. Three composite experiments were conducted by applying herbicides, alone or in combinations. Experiments 1 and 2 were conducted in Palotina, State of Paraná (PR), Brazil. Experiment 3 in Iporã, PR, Brazil. The three during fall 2017 in fallow areas after soybean harvest. The experiment was a randomized complete block design with 4 replications and weed control at 7, 14, 21, 28, 35, and 42 days after application (DAA). The control of R. brasiliensis and C. benghalensis was evaluated in the three experiments, the control of C. sumatrensis, in experiments 1 and 2, while the control of D. insularis was evaluated only in experiment 3. Data were subjected to analysis of variance and F-test (p < 0.05). The treatment means values of experiments 1 and 2 were compared by Tukey's test (p < 0.05), and the treatment mean values of experiment 3 were grouped by the Scott and Knott test (p < 0.05). Some herbicide combinations were effective in controlling R. brasiliensis, C. benghalensis, in a single or sequential application. Herbicide combinations were effective in controlling C. sumatrensis with sequential application. Herbicide combinations in a single application did not provide satisfactory final control (≥ 80%) for D. insularis.

Growth inhibition of sourgrass as a function of period of darkness after diquat application

Photosystem-inhibiting herbicides, such as diquat, act by inducing oxidative stress. However, oxidative damage impairs translocation, resulting in regrowth of the plants. The aim was to evaluate the effectiveness of diquat in controlling the growth of sourgrass exposed to different periods of darkness after application of the herbicide, as well as to evaluate the photosynthetic activity and the production of reactive oxygen species. Two experiments (field and greenhouse) were conducted by applying diquat (200 g a.i. ha-1) on sourgrass plants at the 3 to 4 tiller stage. The treated plants were subjected to different periods of darkness after diquat application (0, 1, 2, 3, 4, 5, and 6 h), in addition to the control treatment without any application. Growth inhibition and mass evaluations of the sourgrass plants were performed in both experiments, whereas photosynthetic activity and H2O2 accumulation in the leaves were evaluated in the greenhouse experiment. The results showed an increase in the sourgrass growth inhibition with an increase in the period of darkness after application. There was a need for a minimum of 6 h of darkness after diquat application to fully inhibit growth (100%) of the sourgrass, whereas plants that remained in the sun since application exhibited less than 50% inhibition. The increase in the period of darkness after diquat application resulted in a reduction in photosynthetic activity and, consequently, lower accumulation of H2O2. Thus, the maintenance of sourgrass in the dark for at least 6 h enables total control of the growth of the plants, preventing regrowth.

Seasonality and forest edge as drivers of Tradescantia zebrina Hort. ex Bosse invasion in the Atlantic Forest / Sazonalidade e efeito de borda florestal como direcionadores da invasão de Tradescantia zebrina Hort. ex Bosse na Mata Atlântica

As a result of biodiversity and ecosystem service losses associated with biological invasions, there has been growing interest in basic and applied research on invasive species aiming to improve management strategies. Tradescantia zebrina is a herbaceous species increasingly reported as invasive in the understory of disturbed forest ecosystems. In this study, we assess the effect of spatial and seasonal variation on biological attributes of this species in the Atlantic Forest. To this end, we measured attributes of T. zebrina associated with plant growth and stress in the four seasons at the forest edge and in the forest interior of invaded sites in the Iguaçu National Park, Southern Brazil. The invasive plant had higher growth at the forest edge than in the forest interior and lower leaf asymmetry and herbivory in the winter than in the summer. Our findings suggest that the forest edge environment favours the growth of T. zebrina. This invasive species is highly competitive in the understory of semi-deciduous seasonal forests all over the year. Our study contributes to the management of T. zebrina by showing that the summer is the best season for controlling this species.

As perdas de biodiversidade e os seus serviços ecossistêmicos ocasionadas pelas invasões biológicas, têm despertado o interesse em pesquisas básicas e aplicadas sobre as espécies invasoras com o objetivo de buscar estratégias de manejo. Tradescantia zebrina é uma das herbáceas crescentemente relatadas como uma invasora no sub-bosque florestal de ecossistemas impactados. Neste estudo, nós estudamos o efeito da variação espacial e sazonal sobre atributos biológicos desta espécie na Floresta Atlântica. Assim, nós mensuramos atributos de T. zebrina associados com o crescimento vegetal e o estresse nas quatro estações do ano em borda e interior da floresta de locais invadidos no Parque Nacional do Iguaçu, Sul do Brasil. A planta invasora apresentou maior crescimento na borda florestal do que no interior. Adicionalmente, assimetria foliar e herbivoria obtidos no inverno foram menores quando comparados ao verão. Nossos achados sugerem que os ambientes de borda florestal favorecem o crescimento de T. zebrina. Esta espécie invasora é altamente competitiva no sub-bosque da Floresta Estacional Semidecídua durante o ano todo. Nosso estudo contribui com o manejo de T. zebrina mostrando que o verão é a melhor estação para o controle desta espécie.

Can a successional crop system associated with preemergent herbicides be a tool to control weeds?

The objective of this research was to evaluate weed control in a successional soybean-sorghum system by using preemergent herbicides. Two trials were conducted in soybean and two in sorghum, in different soil types (sandy in Rio Verde city and clayey in Montividiu city). All trials were established in a completely randomized block design with five preemergent herbicides in soybean (rates in): diclosulam 35.3 g a.i.·ha­1, chlorimuron 20 g a.i.·ha­1, sulfentrazone 200 g a.i.·ha­1, flumioxazin 50 g a.i.·ha­1, S-metolachlor 1728 g a.i.·ha­1, and two controls (hand weeded and untreated). Treatments in sorghum trials were the same to the soybean plus atrazine 1250 g a.i.·ha­1 and atrazine 1250 g a.i.·ha­1 + S-metolachlor 1728 g a.i.·ha­1. All treatments had four replicates. Weed control was assessed at 7, 14, 21 and 28 days after planting (DAP) in both crops. In addition, yield was measured when grains reached physiological maturity. All preemergent herbicide treatments successfully controlled weeds, specially Commelina benghalensis, Cenchrus echinatus and Eleusine indica, in both soybean trials until 28 DAP. In some weeds of sorghum, sulfentrazone, diclosulam and chlorimuron sprayed at soybean preemergence performed better than atrazine sprayed at sorghum preemergence. All preemergent herbicides sprayed at soybean preemergence did not affect soybean and sorghum yield, showing similarity with the hand weeded treatment. The results of this research provide evidence that the mix of crop succession and preemergent herbicide applications can be a strong strategy for integrated weed management.

Effects of ultra high dilution of paraquat 30 ch on growth, chlorophyll content and yield of rice crop

The application of synthetic fertilizers reduces the natural fertility of the soil and contaminates groundwater. Some photosynthesis inhibitors at ultra-high dilution (UHD) increase photosynthesis, growth, and yield of crops. A weedicide Paraquat at UHD enhanced the growth and yield of potatoes in fields. The objective is to see whether the UHD of Paraquat is also effective on rice. This weedicide was serially diluted with distilled water and manually succussed in 30 steps following the preparation of homeopathic dilutions called potencies. In this way, the 30thpotency of Paraquat called Paraquat 30 cH was prepared and preserved in 90 % ethanol. Paraquat 30 cH was diluted with water 1:1000 (v/v) and sprayed on rice plants in a field measuring 0.3125 acres. The control plot of the same area was situated 300 meters away from the test plot. Three treatments were given at an interval of 7 days. The treated plot showed increased growth, chlorophyll content, and rice yield significantlycompared to control. The UHD of the weedicide produced precisely the opposite effect of the crude material on plants. The increased growth and yield of rice by Paraquat 30 cH may be due to the enhancement of photosynthesis of treated plants. The UHD of Paraquat increased the yield of rice by 19.35% over the control.

Agronomic characterization of sunflower cultivars for animal feeding in tropical conditions

This study was developed to examine morpho-agronomic traits of 18 sunflower cultivars and identify superior cultivars in terms of grain yield, forage quality, or both, for animal feeding. Twenty-two morpho-agronomic traits related to plant development and architecture; earliness of maturity; grain yield (achenes); dry matter yield; and dry matter content were evaluated. Cultivars Hélio 253, Hélio 358, Embrapa 122, BRS 321, and Hélio 360 showed inflorescence at the final stage. Aguará 4 showed the lowest flowering rate, characterizing it as late-maturing. For grain yield, cultivars Charrua, Olisun 3, BRS 321, Paraíso 103CL, Paraíso 65, Aguará 6, and CF 101 are recommended, as they showed the highest achene yields (average: 1,541.67 to 2,148.81 kg.ha−1, respectively). Cultivars Charrua, Hélio 251, Olisun 3, Hélio 360, Paraíso 55, and Paraíso 103CL exhibited higher dry matter yields (9,550.93 to 11,789.91 kg ha−1) and were thus indicated for forage production. Cultivars Charrua, Olisun 3, BRS 321, Paraíso 103CL, Paraíso 65, Aguará 6, and CF 101 are recommended for grain yield, for the diet of monogastric animals; Charrua, Hélio 251, Olisun 3, Hélio 360, Paraíso 55, and Paraíso 103CL for forage yield, for ruminant feeding; and Charrua, Olisun 3, and Paraíso 103CL for both purposes.

Chemical management of Cyperus rotundus L. and other weeds at sugarcane in PSS system

Among the main weeds with difficult to control in the sugarcane fields can be cited purple nutsedge (Cyperus rotundus L.). This specie was observed in the seed bank in sugarcane fields harvested with or without burning. The objective of this study was to evaluate the efficacy of herbicides in pre-sprouted seedlings (PSS) of sugarcane in the control of C. rotundus and other weeds. The work was carried out in the field, in a randomized complete block design, and four replications. The treatments corresponded to the herbicides applied in pre-planting: sulfentrazone (800 g a.i. ha-1), diclosulam (193.17 g a.i. ha-1), imazapic (133 g a.i. ha-1) and imazapyr (500 g a.e. ha-1); post-planting: halosulfuron (112.5 g a.i. ha-1), ethoxysulfuron (135 g a.i. ha-1), MSMA (1,975 g a.i. ha-1) and 2,4-D (1,340 g a.e. ha-1); besides a control treatment weeding and another without weeding. The symptoms of injury on sugarcane plants, percentage of weed control, variables related to agronomic performance of sugarcane, and yield were evaluated. The herbicides diclosulam, imazapic, and imazapyr caused serious damage to the crop. The halosulfuron, ethoxysulfuron, MSMA, and 2,4-D did not cause symptoms of injury to sugarcane, however, the treatments had a reduced yield due to the low weed control. The sulfentrazone treatment obtained the second highest yield but with effective weed control (>70%) up to 45 days after planting. The best controls were obtained with pre-planting treatments; however, herbicide positioning studies should be performed in relation to PSS.

Herbicide performance in the control of Conyza spp. where three plant heights

Intensive use of the herbicide glyphosate has led to herbicide resistant Conyza spp. populations. Thus, there is a need to indicate alternative herbicides and the appropriate developmental stage for controlling these populations. This study identifies alternatives for controlling glyphosate-resistant horseweed, with treatment applications at different plant heights. For this purpose, field experiments were conducted in the 2016/17 and 2017/18 crop years. The evaluated treatments were: glyphosate (540 g ae ha-1), glyphosate (1080 g ae ha-1), glyphosate (2160 g ae ha-1), glyphosate (3240 g ae ha-1), glyphosate + 2.4-D (1080 + 1005 g ae ha-1), glyphosate + saflufenacil (1080 + 49 g ae/ai ha-1), paraquat (400 g ai ha-1), diquat (400 g ai ha-1), ammonium glufosinate (600 g ai ha-1), and control (without application). These treatments were applied to plants with a maximum of 5 cm; plants between 6 and 15 cm; and plants between 16 and 25 cm. The results showed that glyphosate did not control weeds, regardless of rate. With the exception of 2,4-D, which needs complementation with sequential application of another contact herbicide, all alternatives were viable for the control of Conyza spp. plants with a maximum height of 5 cm.

Adjuvant interference on spray solution properties of 2, 4 - D and dicamba herbicides and their efficacy for Ipomoea SPP. control / Interferência de adjuvantes nas propriedades de calda dos herbicidas 2, 4 - D e dicamba e sua eficácia no controle de Ipomoea SPP

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.

Os herbicidas mimetizadores da auxina constituem alternativas importantes para o manejo de plantas daninhas de difícil controle, como Ipomoea spp. Sabe-se que o uso de adjuvante afeta positivamente a eficácia biológica dos pesticidas, modificando as principais propriedades da solução e do espectro de gotas da pulverização. Os objetivos desse trabalho foram determinar em que medida o uso de adjuvantes pode alterar os parâmetros da solução de pulverização e afetar a eficiência dos herbicidas mimetizadores da auxina para Ipomoea spp. Os estudos foram conduzidos em duas fases: em laboratório e em campo. Em laboratório foi avaliado o pH, tensão superficial e características das gotas dos herbicidas. Em campo foi avaliado o controle da planta daninha. Todos os adjuvantes modificaram as propriedades da solução de pulverização, diminuindo os valores de tensão superficial. A maioria dos adjuvantes diminuiu os valores de pH, bem como o número e a densidade de gotas. Independentemente do uso de adjuvante, os níveis de controle de Ipomoea spp. aumentaram mais rapidamente após a pulverização com 2,4-D do que com o dicamba, resultando em menor acúmulo de biomassa quando o primeiro foi usado. Os tratamentos contendo dicamba apresentaram ligeiramente menor controle de Ipomoea spp. A aplicação de 2,4-D promoveu menor biomassa e maiores níveis de controle em relação ao dicamba de Ipomoea spp., sugerindo que possa constituir uma opção melhor de controle. Embora a eficácia do herbicida não tenha sido melhorada com adjuvantes, seu uso ainda deve ser considerado com alterações favoráveis da solução de pulverização, principalmente tamanhos de gotas em qualquer uso de pontas de pulverização - mantendo a eficácia do controle de plantas daninhas.

Análise dos efeitos do glifosato e sua formulação Roundup® nas células e gônadas dos peixes Danio rerio (Cyprinidae) / Analysis of the effects of glyphosate and its formulation Roundup® on the cells and gonads of fish Danio rerio (Cyprinidae)

Os herbicidas estão entre os insumos químicos mais utilizados na agricultura e apresentam ação toxicológica para as plantas. Dentre os herbicidas existentes, o glifosato e a sua formulação comercial Roundup® são os mais utilizados devido à eficácia no controle de ervas daninhas. Entretanto, estudos sugerem que estes herbicidas podem provocar distúrbios a organismos aquáticos, principalmente o Roundup®, que além do glifosato ativo, apresenta na composição componentes surfactantes que aumentariam o seu potencial toxicológico para os seres vivos. Desta forma, o presente estudo teve como objetivo comparar o potencial mutagênico e desenvolvimento gonadal do princípio ativo glifosato e sua formulação Roundup® em peixes Danio rerio. Para isso, exemplares adultos de D. rerio permaneceram em aquários expostos à concentração de 65 µg/L de cada herbicida. Foram realizadas contagens de micronúcleos, calculado o índice gonadossomático (IGS) e verificado os estágios de maturação gonadal. Os resultados demonstraram que os peixes expostos aos herbicidas apresentaram aumentos significativos na frequência de micronúcleos, bem como no IGS, e maior ocorrência de ovários com estágios em maturação e maduros. Não foram verificadas diferenças significativas na comparação dos herbicidas, exceto um aumento na frequência de ovários maduros nas fêmeas expostas ao glifosato. Observou-se que, mesmo em pequenas concentrações, os herbicidas poderiam ter ocasionado efeitos nocivos para os peixes D. rerio, podendo induzir efeitos clastogênicos nos eritrócitos, assim como distúrbios reprodutivos, aumentando a preocupação sobre os impactos que estes herbicidas podem acarretar sobre o ciclo de vida destes organismos.(AU)

The herbicides are among the most used chemical inputs in the agriculture and present a great toxicological action for the plants. Among the existing herbicides, glyphosate and its commercial formulation Roundup® are the most used due to their effectiveness in control of weeds. However, studies suggest that these herbicides can cause disturbances to aquatic organisms, mainly the Roundup®, that besides active glyphosate, it presents in the composition components surfactants that would increase its toxicological potential for the alive beings. Therefore, the aim of this study is to compare the mutagenic potential and gonadal development of the active principle glyphosate and its formulation Roundup® in fish Danio rerio. Thus, adult copies of D. rerio stayed in aquariums exposed to a concentration of 65 µg / L of each herbicide. Micronucleus counts were performed and the Gonadossomatic index (GSI) was calculated and the stages of gonadal maturation were verified. The results demonstrated that the fish exposed to the herbicides, presented significant increases in the micronucleus frequency, as well as in GSI and larger occurrence of ovaries with stages in maturation and mature. There were no significant differences in herbicide comparison, except an increase in the frequency of mature ovaries in the exposed females to glyphosate. It was observed that even in small concentrations, the herbicides could presented harmful effects for the fish D. rerio, could have caused clastogenic effects in the erythrocytes, as well as, reproductive disturbances, increasing the concern about the impacts that these herbicides can have on the life cycle of these organisms.(AU)

Herbicide management in glyphosate and sulfonylurea-tolerant soybeans / Manejo de herbicidas em soja tolerante a glifosato e sulfonilureias

There is little information on the efficacy and selectivity of sulfonylureas, isolated and in association with glyphosate, in glyphosate and sulfonylurea-tolerant soybeans. Thus, the present study aims to evaluate the efficacy of weed control and selectivity of sulfonylureas, isolated and in association with glyphosate, at post-emergence (V4) of RR2/STS soybean. The experiments were conducted in the in areas located in Piracicaba City, São Paulo State (SP), Brazil (experiment I) and Palotina City, Paraná State (PR), Brazil (experiment II). Treatments were composed of application of the herbicides sulfometuron, chlorimuron, halosulfuron, ethoxysulfuron and glyphosate, isolated and in association, in the BMX Garra RR2/STS cultivar. Experiment I was conducted focusing on the evaluation of the efficacy of weed control; whereas experiment II focused mainly on the evaluation of herbicide selectivity. The experimental design was the randomized complete block, with four replications. Crop injury, weed control, and variables related to agronomic performance were evaluated. Data were submitted to analysis of variance, and the means of the treatments were compared with the Tukey test. Sulfonylureas in association with glyphosate were effective in weed control and selective for the BMX Garra RR2/STS soybean cultivar. The sulfometuron + chlorimuron + glyphosate association presented phytotoxic potential for the BMX Garra RR2/STS cultivar.(AU)

Há poucas informações sobre a eficácia e seletividade de sulfonilureias, isoladas e associadas ao glifosato, na soja tolerante ao glifosato e às sulfonilureias. Assim, o presente estudo teve como objetivo avaliar a eficácia no controle de plantas daninhas e seletividade de sulfonilureias, isoladas e em associação com o glifosato, em pós-emergência (V4) de soja RR2/STS. Os experimentos foram conduzidos em áreas localizadas nos municípios de Piracicaba, São Paulo (SP), Brasil (experimento I) e Palotina, Paraná (PR), Brasil (experimento II). Os tratamentos foram compostos pela aplicação dos herbicidas sulfometurom, clorimurom, halossulfurom, etoxissulfurom e glifosato, isolados e em associação, no cultivar BMX Garra RR2/STS. O experimento I foi realizado com o foco principal na avaliação da eficácia no controle de plantas daninhas; ao passo que o experimento II se concentrou principalmente na avaliação da seletividade dos herbicidas. O delineamento experimental foi o de blocos casualizados, com quatro repetições. Foram avaliados sintomas de injúria, controle de plantas daninhas e variáveis relacionadas ao desempenho agronômico. Os dados foram submetidos à análise de variância, e as médias dos tratamentos foram comparadas pelo teste de Tukey. Sulfonilureias associadas ao glifosato foram eficazes no controle de plantas daninhas e seletivas para o cultivar de soja BMX Garra RR2/STS. A associação sulfometurom + clorimurom + glifosato apresentou potencial fitotóxico para o cultivar BMX Garra RR2/STS.(AU)

Viability of Cyperus rotundus L. tubers after application of herbicide in pre- and postemergence / Viabilidade de tubérculos de Cyperus rotundus L. após a aplicação de herbicidas em pré e pós-emergência

Chemical management is the most widely adopted technique to control weeds in sugarcane crops. Purple nutsedge (Cyperus rotundus L.) is among the most difficult species to control. Herbicides need to be absorbed and translocated in a sufficient amount for the tuber chain to be effective. Thus, this study aimed to evaluate the effectiveness of the herbicides sulfentrazone, diclosulam, imazapic, imazapyr, halosulfuron, ethoxysulfuron, monosodium methyl arsenate (MSMA), and 2,4-dichlorophenoxyacetic acid (2,4-D) in controlling C. rotundus and reducing the viability of its tubers. The experiment was carried out in a greenhouse in a completely randomized design, with nine treatments and four replications. The herbicides sulfentrazone (800 g active ingredient ­ ai·ha?1), diclosulam (193.17 g ai·ha?1), imazapic (133 g ai·ha?1), and imazapyr (500 g acid equivalent ­ ae·ha?1) were applied in preemergence at five days after planting the tubers, while halosulfuron (112.5 g ai·ha?1), ethoxysulfuron (135 g ai·ha?1), MSMA (1,975 g ai·ha?1), and 2,4-D (1,340 g ae·ha?1) were applied in postemergence (4 to 5 leaves). The parameters visual control, shoot dry matter, number of tubers and bulbs, weight of tubers + bulbs, number of epigeal manifestations, and tuber viability were analyzed. The herbicides diclosulam, halosulfuron, and ethoxysulfuron provided 100% control of the shoot at 90 days after application (DAA). All herbicides reduced the number of bulbs, weight of tubers + bulbs, and shoot dry matter. The herbicides sulfentrazone, imazapic, halosulfuron, ethoxysulfuron, and MSMA provided the highest reduction in tuber viability.(AU)

O manejo químico é o mais adotado para o controle de plantas daninhas na cultura da cana-de-açúcar. Entre as espécies de difícil controle está a tiririca (Cyperus rotundus L.). Os herbicidas utilizados precisam ser absorvidos e transportados para a cadeia de tubérculos em quantidades suficientes para serem eficazes. Assim, objetivou-se com este estudo avaliar a eficácia dos herbicidas sulfentrazona, diclosulam, imazapique, imazapir, halossulfurom, etoxissulfurom, metano arseniato ácido monossodico (MSMA) e ácido diclorofenoxiacético (2,4-D) no controle de C. rotundus e na redução da viabilidade de seus tubérculos. O experimento foi realizado em casa de vegetação, em delineamento inteiramente randomizado, com nove tratamentos e quatro repetições. Os herbicidas sulfentrazone (800 g ingrediente ativo ­ i.a.·ha-1), diclosulam (193,17 g i.a.·ha-1), imazapique (133 g i.a.·ha-1) e imazapir (500 g equivalente ­ e.a.·ha-1) foram aplicados cinco dias após o plantio dos tubérculos em pré-emergência, enquanto que o halossulfurom (112,5 g i.a.·ha-1), etoxissulfurom (135 g i.a.·ha-1), MSMA (1.975 g i.a.·ha-1) e 2,4-D (1.340 g e.a.·ha-1) foram aplicados em pós-emergência (4 a 5 folhas). Foram feitas avaliações visuais de controle, massa seca da parte aérea, número de tubérculos e bulbos, peso de tubérculos + bulbos, número de manifestações epígeas e viabilidade de tubérculos. Aos 90 dias após a aplicação (DAA) os herbicidas diclosulam, halossulfurom e etoxissulfurom propiciaram 100% de controle da parte aérea. Todos os herbicidas reduziram o número de bulbos, peso de tubérculos + bulbos e massa seca da parte aérea. Sulfentrazona, imazapic, halossulfurom, etoxissulfurom e MSMA foram os herbicidas que mais reduziram a viabilidade dos tubérculos.(AU)

Weed management in glyphosate-resistant maize / Manejo de plantas daninhas em milho resistente ao glifosato

The application of glyphosate associated with other herbicides is an important alternative for weed control in maize, to increase control spectrum and to minimize problems with resistance and tolerance from some species to the product. The objective of this work was to evaluate the efficacy, selectivity and effects on the grain yield components of glyphosate-resistant maize as a function of its application, associated or not with other pre- and postemergence herbicides. The design used was randomized blocks with four replications. Treatments consisted in the use of glyphosate combined with the herbicides: atrazine, [atrazine + simazine], [atrazine + oil], [atrazine + S-metolachlor], applied pre- and/or postemergence and [nicosulfuron + mesotrione] only postemergence, plus two controls, one weeded and one infested. The evaluated variables were maize phytotoxicity, weed control, ear insertion height, number of rows per ear, number of grains per row, one thousand grain mass and grain yield. Herbicide treatments caused low phytotoxicity to maize, less than 6%; control greater than 88, 95 and 95% for alexandergrass, turnip and sunflower, respectively, and did not affect grain yield components. The tested herbicides are selective to the hybrid Forseed 2A521 PW and effective in weed control. Weed control with weeding or herbicide increased maize Forseed 2A521 PW yield by 43%. The association of glyphosate with pre- or postemergence herbicides increased maize grain yield by approximately 14%.(AU)

O uso de glifosato associado com outros herbicidas torna-se uma alternativa importante para o manejo de plantas daninhas infestantes do milho, pois ele aumenta o espectro de controle, minimiza problemas com resistência e tolerância de plantas daninhas ao herbicida. O objetivo deste trabalho foi estudar a eficiência, a seletividade e os efeitos nos componentes de rendimento de grãos do milho resistente ao glifosato pelo uso dessa substância associada ou não a outros herbicidas aplicados em pré- e pós-emergência. O experimento foi instalado em delineamento de blocos ao acaso, com quatros repetições. Os tratamentos consistiram na utilização do glifosato em combinação com os herbicidas: atrazina, [atrazina + simazina], [atrazina + óleo], [atrazina + S-metolacloro], aplicados em pré- e/ou pós-emergência e o [nicosulfuron + mesotriona] somente em pós-emergência, além das testemunhas capinada e infestada. Avaliaram-se as variáveis: fitotoxicidade ao milho, controle de plantas daninhas, altura de inserção de espigas, número de fileiras e de grãos por espiga, peso de mil grãos e a produtividade de grãos. Os herbicidas ocasionaram baixa fitotoxicidade ao milho, inferior a 6%, controle superior a 88, 95 e 95% para papuã, nabo e girassol, respectivamente, e não influenciaram negativamente nos componentes relacionados ao rendimento de grãos da cultura. Os herbicidas testados são seletivos ao híbrido Forseed 2A521 PW e efetivos no controle de papuã, nabo e girassol. O manejo das plantas daninhas com capina ou herbicidas proporcionou aumento de cerca de 43% na produtividade de grãos do híbrido de milho Forseed 2A521 PW. O uso de glifosato em mistura de tanque com herbicidas aplicados em pré- ou pós-emergência incrementou, aproximadamente, 14% a produtividade de grãos de milho.(AU)

Decomposition of cover crop mulch and weed control under a no-till system for organic maize / Decomposição da palhada e controle de plantas daninhas em plantio direto orgânico de milho

The decomposition dynamics of cover crop mulch influence the nutrient supply of successor crops and weed suppression. This is even more relevant in organic production systems, due to their limited use of chemical fertilizers and herbicides. As such, the aim of this study was to quantify biomass production, model the decomposition and N, P and K release of the mulch of different cover crops, and assess the weed suppression of cover crops in the form of mulch and in consortium with organic maize. A randomized block design was used, with a 7x2 factorial scheme (7 cover crop management strategies and 2 cropping systems - maize in monoculture and intercropped with jack bean) and 4 replicates. The management practices that produced the most biomass were white lupine intercropped with black oat and the white lupine, black oat and sunflower monocultures. The use of cover crops did not differ from manual weeding in terms of weedbiomass, but did affect the relative importance (RI) of nutgrass. Additionally, maize intercropped with jack bean reduced weed biomass in subsequent crop growth stages.

A dinâmica de decomposição da palhada de plantas de cobertura influencia o suprimento de nutrientes para a cultura sucessora e a supressão de plantas daninhas. Desse modo, o objetivo deste estudo foi quantificar a produção de biomassa e de modelar a decomposição e liberação de N, P e K da palhada de diferentes plantas de cobertura, assim como, avaliar a supressão de plantas daninhas por plantas de cobertura na forma de palhada e em consórcio com milho orgânico. O experimento foi realizado em esquema fatorial 7 x 2 (7 tipos de manejos de planta de cobertura e 2 sistemas de cultivo ­ milho em monocultivo e consorciado com feijão-de-porco) em blocos ao acaso com 4 repetições. Os manejos que produziram a maior biomassa foram os consórcios de tremoço branco e aveia preta, além dos monocultivos de tremoço branco, aveia preta e girassol. Os manejos de planta de cobertura não se diferenciaram do manejo com capina manual para biomassa de plantas daninhas, porém afetaram a importância relativa da tiririca. Já o consórcio de milho com feijão-de-porco diminuiu a biomassa de plantas daninhas em estádios avançados da cultura.