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ABSTRACT: Weed species is one of the factors contributing to grain yield losses due to crop-weed competition. Two of the most common weeds of soybean fields in Brazil are from the Rubiaceae family: Borreria latifolia and Richardia brasiliensis. This study aimed to evaluate the effects of B. latifolia and R. brasiliensis on plant development, yield components, and soybean productivity. Two assays were conducted in a randomized block design with four replications, using a two-level factorial design, in which the first factor consisted of the species B. latifolia and R. brasiliensis and the second factor consisted of the densities 0, 2, 4, 6, 8, 10, and 12 plants m-2. Plant height, leaf area and total chlorophyll in the V6 and R5 stages, number of pods per plant, number of grains per pod, 1000-grain weight, and grain yield loss were evaluated in both cultivars. Grain yield of both soybean cultivars was negatively affected by the interference with B. latifolia and R. brasiliensis. The species B. latifolia was more competitive with soybean when compared to R. brasiliensis, causing higher reductions for all variables. Each B. latifolia plant per square meter is able to reduce the yield of soybean by 3 a 4.4%, while each R.brasiliensis plant reduces yield by 2 a 2.6%. For both species, the reduction in soybean yield due to competition was caused by a decrease in the number of pods per plant, number of grains per pod, and 1000-grain weight.

ABSTRACT: The combination of herbicides and other pesticides can influence weed and crop management. This study aimed to evaluate the response of the combination of different herbicides with insecticides or fungicides of different chemical groups on the development and yield of wheat grains of the cultivar ORS Vintecinco. The experimental design was a randomized block design with three replications. The experiment consisted of 33 treatments, as follows: control without application and application of the herbicides 2,4-D (1,005 g a.e. ha-1), bentazon (756 g a.i. ha-1), metsulfuron-methyl (3 g a.i. ha-1), and pyroxsulam (16 g a.i. ha-1), isolated or combined with the insecticides chlorfluazuron (15 g a.i. ha-1), chlorpyrifos (720 g a.i. ha-1), deltamethrin (5 g a.i. ha-1), and methomyl (5 g a.i. ha-1) or with the fungicides azoxystrobin (100 g a.i. ha-1), carbendazim (250 g a.i. ha-1), and propiconazole (190 g a.i. ha-1). Relative tolerance (RT), shoot dry matter (SDM), yield components, and grain yield were evaluated. In general, pyroxsulam had the highest number of synergistic interactions with insecticides and fungicides, reducing RT and SDM, especially the combination pyroxsulam + chlorpyrifos due to a lower RT level (45%) and higher SDM reduction (52%). All combinations of herbicides with the insecticide chlorpyrifos and most of the combinations with the fungicide propiconazole led to a reduction of grain yield when compared to their isolated application or to control without application.

ABSTRACT: Persistence of an herbicide is defined as the ability to maintain the integrity of its molecule and chemical, physical, and phytotoxic properties in the environment where it was applied. Knowledge of persistence has implications both for the toxicity generated on species grown in succession and for the period in which the herbicide controls weeds. This study aimed to assess the persistence of the herbicide saflufenacil in an Oxisol by means of bioassays. Two experiments with the application of 29.4 g ha-1 of saflufenacil were carried out under field conditions: the first in the 2011/2012 season and the second in the 2012/2013 season. Soil samples were collected at depths of up to 10 cm at different times after application. Subsequently, two bioassays were carried out in a greenhouse by using beet (Beta vulgaris L.) and cucumber (Cucumis sativus L.) as bioindicators. The studies were carried out in a completely randomized design with four replications. Treatments consisted of periods after saflufenacil application (0, 5, 10, 15, 25, 35, 50, and 100 days). The crop was also considered as a factor. Stand, height, and phytotoxicity of plants were assessed in both agricultural seasons at 14, 21, and 28 days after sowing (DAS), as well as shoot fresh (SFM) and dry matter (SDM) at 28 DAS. In general, saflufenacil persistence was between 25 and 35 days. Beet was more sensitive to the presence of saflufenacil in the soil when compared to cucumber. Herbicide effects were higher in the 2012/2013 season when compared to the 2011/2012 season.

ABSTRACT Weed resistance to herbicides is a major global problem for agriculture. In recent years, the increased use of herbicides, without proper planning, has led to a large increase in the number of cases of weed biotypes that are resistant to one or more herbicide mechanism of action. Wild poinsettia biotypes (Euphorbia heterophylla), discovered in the State of Paraná, with resistance to herbicides that inhibit protoporphyrinogen oxidase (PROTOX) and acetolactate synthase (ALS), are the first case to exhibit multiple resistance in Brazil. This study analyzed the genetic inheritance of PROTOX inhibiting herbicide resistance in E. heterophylla. Crosses were conducted between biotypes that were susceptible (female parent) and those carrying multiple resistance to ALS and PROTOX inhibitors (male parent) to obtain the F1 generation. Backcrosses were performed (RC1 and RC2) and the F1 generation was advanced to F2. F1, F2, RC1, RC2 generation plants and their parents were subjected to applications of the herbicide fomesafen (250 g i.a. ha-1). The observed frequencies in the F2 generation were not different from the expected frequency of 3:1. All RC2 individuals were resistant, while the RC1 population showed a 1:1 segregation, which would be expected when a single gene controls the trait. Thus, it can be inferred that E. heterophylla resistance to PROTOX-inhibiting herbicides is conditioned by a single and dominant nuclear gene.

ABSTRACT The objectives of this study were to determine the effect of herbicide ethoxysulfuron on the development of commom bean (Phaseolus vulgaris), to evaluate the impact of the herbicide on the crop grain yield and to determine the mechanism of tolerance of common bean to ethoxysulfuron. Field experiments were carried out with several doses of ethoxysulfuron to determine its effect on the grain yield of two varieties of common bean ("IPR Andorinha", "IPR Tangará"). The mechanism of plant tolerance was evaluated through several methods, including the analysis of the ALS enzyme sensitivity to herbicide and the use of P450 inhibitors (the insecticides malathion + chlorpyrifos) and the use of antidote (mefenpyr-diethyl). When the rate of ethoxysulfuron was 83.2 g ha-1, the grain yield loss reached 25% (IPR Tangará) and 35% (IPR Andorinha). The ALS enzyme activity was severely reduced even at low concentrations ethoxysulfuron (1 μM), indicating that the mechanism of tolerance is not the insensitivity of the herbicide target enzyme. The inhibitors of herbicide detoxification increased the sensitivity of the bean plants to ethoxysulfuron, and the antidote (stimulator of herbicide degradation) mitigated the herbicidal effect. These results strongly support the hypothesis that the mechanism of tolerance of common bean plants to ethoxysulfuron is enhanced herbicide detoxification.

ABSTRACT This study was conducted to evaluate the efficacy of joyweed (Alternanthera tenella) control and antagonistic or synergistic potentials of saflufenacil herbicide applied alone or tank mixed with paraquat, metribuzin and clomazone. The experiment was conducted in a greenhouse in a completely randomized design with four replications. Treatments consisted of saflufenacil herbicide doses (0, 0.4, 0.7, 1.4, 2.1 and 2.8 g ha-1) applied isolated or associated with paraquat (0, 1 and 3 g ha-1), metribuzin (0, 38.4 and 105.6 g ha-1) or clomazone (0, 288 and 504 g ha-1). Visual control was determined at 14 and 21 days after spraying the herbicides (DAA) and shoots dry matter at 21 DAA. Colby's method was used to calculate the response from herbicide interactions. Saflufenacil associations with paraquat and metribuzin were promising to control A. tenella, due to the high levels of control achieved and because they demonstrated compatibility, especially in some combinations. Tank mixing saflufenacil with clomazone was not promising for the control of A. tenella due to the low efficacy of joyweed control and because it demonstrated herbicide incompatibility.

ABSTRACT: The characteristics of multiple resistance in Euphorbia heterophylla biotypes to herbicides that are inhibitors of ALS (Acetolactate synthase) and PPO (Protoporphyrinogen oxidase) and their responsible mechanisms are still not completely elucidated. The objectives of this study were to identify cross-resistance to herbicides from different chemical groups of ALS inhibitors (imidazolinones, sulfonylureas, pyrimidyl benzoates and sulfonanilides) and also PPO inhibitors (diphenylethers, phthalamides, oxadiazoles, triazolinones and pyrimidinediones) in E. heterophylla biotypes with multiple resistance to these herbicides; to analyze whether the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) constitute mechanisms that are responsible for the resistance to PPO inhibitors. Initially, the response to doses of herbicides from these different chemical groups was determined, using doses below and above the one recommended for the species. The control of E. heterophylla was determined, estimating the required doses for a 50 and 80% control reduction and calculating the resistance factors. The constitutive and induced activities of the SOD and POD enzymes were also determined. The results confirmed cross-resistance for all chemical groups of ALS and PPO inhibitors in the Bom Sucesso do Sul and Vitorino biotypes. The constitutive and induced activities of the SOD and POD enzymes were superior in plants from the E. heterophylla biotypes Vitorino and Bom Sucesso do Sul, contributing to their resistance to PPO inhibiting herbicides.

ABSTRACT: Infesting species of Rubiaceae family have great importance in soybean crops in Southwest of Paraná and North of Santa Catarina, especially due to the selection of tolerant populations caused by the pressure of selection exerted by intensive use of glyphosate. The study aimed to evaluate the levels of tolerance to glyphosate in biotypes of broadleaf buttonweed (Borreria latifolia) (BL) and white-eye (Richardia brasiliensis) (RB) by means of dose-response curves. Two experiments were conducted in a greenhouse, in completely randomized design (CRD), with four replications. Fourteen BL biotypes and eleven RB biotypes were evaluated, collected in soybean fields of Paraná and Santa Catarina. The doses of glyphosate were 0, 74, 163, 360, 792 and 1,742 g ha-1, applied when the plants had 6 to 8 leaves. Visual control was evaluated at 14 and 28 days after application (DAA), as well as mass of green shoots and mass of dry shoots at 28 DAA. It was verified that there is response variability among the biotypes studied. BL biotypes 277, 283 and 300, and RB biotypes 283, 285 and Papanduva were not controlled with glyphosate at doses superior to those normally used in crops (720 g ha-1), indicating selection by the recurrent use of glyphosate. The tolerance factors ranged from 1.1 to 4.1 and 2.8 to 8.1 for RB and BL, respectively. The greatest difficulties of control were reported in areas where RR technology had been adopted for more than six years.

ABSTRACT: Synergism is a desired result in the interaction between herbicides because it provides many benefits, among which the reduction of doses and the increment of control efficiency, and because it positively signals for the joint application of herbicides. The objective of this study is to evaluate the effect of the association of saflufenacil with other herbicides that promote oxidative stress on the development of Euphorbia heterophylla as well as to analyze if the resulting interactions are antagonistic, additive or synergistic. The experiment was conducted in pots, in a greenhouse, using a completely randomized design with four replications. Treatments consisted of saflufenacil (0, 1,2, 2,32, 4,47, 8,63, 16,65 g ha-1) alone and associated with clomazone (288 and 504 g ha-1), metribuzin (105.6 and 206.4 g ha-1) and paraquat (20 and 40 g ha-1), as well as these herbicides applied alone at the same doses described above. Twenty-one days after the application (DAA), the shoot dry matter (SDM) of plants was evaluated in each experimental unit. The Limpel-Colby method was used to calculate the expected response of the herbicide interaction. All combinations of saflufenacil with clomazone, metribuzin and paraquat were considered synergistic. Among the treatments associated with saflufenacil, those including metribuzin at the dose of 105.6 g ha-1 were the ones that provided the most promising results, which stood out for the greater reductions of wild poinsettia shoot dry matter, compared to the application of saflufenacil alone.

ABSTRACT: In literature, there are few studies evaluating the response of different bean cultivars to herbicides, particularly the ALS enzyme inhibitors. The objective of this study was to evaluate the selectivity of common bean cultivars to the herbicide ethoxysulfuron and to select cultivars that are more tolerant to it. An experiment was conducted in a greenhouse, in a completely randomized experimental design with four replications. Factors consisted in 20 bean cultivars (IPR Eldorado, IPR Siriri, IPR Gralha, IPR 81, IPR Uirapuru, IPR Colibri, IPR Tuiuiú, BRS Esplendor, IPR Tangará, IPR Juriti, IPR Corujinha, IPR Andorinha, IPR Curió, BRS Campeiro, BRS Pérola, BRS Notável, BRS Estilo, UTF 3, UTF 5 e UTF 6), and four doses of ethoxysulfuron (0, 50, 100 and 200 g ha-1) were used. At the dose of 200 g ha-1, the reduction of the shoot dry matter of plants ranged from 30 to 80%, indicating that there was high variability in the response of bean cultivars to the herbicide. The bean cultivars classified as more tolerant to ethoxysulfuron are: IPR 81, IPR Uirapuru, BRS Estilo, IPR Gralha and BRS Pérola, while the less tolerant cultivars are: IPR Eldorado, IPR Tuiuiú, IPR Tangará, IPR Curió, UTF 3, UTF 5 and BRS Esplendor.

Mobility of atrazine in soil has contributed to the detection of levels above the legal limit in surface water and groundwater in Europe and the United States. The use of new formulations can reduce or minimize the impacts caused by the intensive use of this herbicide in Brazil, mainly in regions with higher agricultural intensification. The objective of this study was to compare the leaching of a commercial formulation of atrazine (WG) with a controlled release formulation (xerogel) using bioassay and chromatographic methods of analysis. The experiment was a split plot randomized block design with four replications, in a (2 x 6) + 1 arrangement. The main formulations of atrazine (WG and xerogel) were allocated in the plots, and the herbicide concentrations (0, 3200, 3600, 4200, 5400 and 8000 g ha-1), in the subplots. Leaching was determined comparatively by using bioassays with oat and chromatographic analysis. The results showed a greater concentration of the herbicide in the topsoil (0-4 cm) in the treatment with the xerogel formulation in comparison with the commercial formulation, which contradicts the results obtained with bioassays, probably because the amount of herbicide available for uptake by plants in the xerogel formulation is less than that available in the WG formulation.

ABSTRACT Grass weeds are common in summer crops and strongly decreases the grain yield of the common bean crop. The time of herbicide application influences the variability of environmental conditions and affects the product performance. The objectives of this work were to identify the time of fluazifop-p-butyl (fluazifop) application which gives best grass weed control in the common bean crop and to elucidate the environmental variables most important for the efficacy of this herbicide. Field experiments were conducted involving five application times (2 a.m., 6 a.m., 11 a.m., 4 p.m. and 9 p.m.) and five doses of fluazifop (80, 110, 140, 170 and 200 g ha-1), with additional no-herbicide control. At the time of the herbicide application it was determined the air temperature, relative humidity, the photosynthetically active radiation (PAR) and the leaf angle, whereas the weed control and the dry mass of the weed Urochloa plantaginea was assessed at 20 days after treatment (DAT). Efficacy on grass control with fluazifop was dependent on the herbicide dose and on the time of day that the product was applied. Spray at early morning hours (6 a.m.) showed better efficacy on weed control in relation to periods during warmer conditions of the day (11 a.m. and 4 p.m.). Nocturnal fluazifop application had better weed control when compared to herbicide sprayed in the afternoon. The air temperature, relative humidity and PAR were correlated to weed leaf angle, which correlated the most with fluazifop performance.

ABSTRACT Tolerance, also referred to as natural resistance, is a feature that exists in the plant even before herbicide application in an area. I. grandifolia, I. indivisa and I. purpurea are among the tolerant species most commonly found over fields in southern Brazil. We hypothesized that the intensive use of glyphosate results in increasing levels of tolerance to glyphosate, and in pronounced response variability in populations of the same Ipomoea species. This study aimed at identifying tolerance variations to glyphosate among I. grandifolia, I.indivisa and I. purpurea morning glory species and among populations of these species. In crops over Paraná and Santa Catarina states (Brazil) 31 biotypes were collected (20I. grandifolia, 7I.indivisa and 4I. purpurea), on which were applied 0, 216, 432, 864, 1,296, 1,728 and 2,160 g a.e. ha-1 of glyphosate and the dose required to reduce 50% of dry matter (GR50) was determined. Biotypes of all tested Ipomoea species showed variability of glyphosate tolerance. Tolerance factors had greater amplitude among biotypes of I. gradifolia and I. indivisa species (between 1.7 and 33.6 and between 3.3 and 34.2, respectively) than in I. purpurea (between 3.7 and 4.9). Especially within I. gradifolia e I. indivisa species, some biotypes required a much higher dose than the recommended one to control the wild biotype, indicating progress in the level of glyphosate tolerance; this proves the initial hypothesis of this work.

Herbicides that inhibit the enzyme protoporphyrinogen oxidase (PROTOX) are usually effective to control dicotyledonous weeds and their agronomic efficacy is affected by environmental and physiological factors. The objective of this review is to summarize the knowledge of those factors available in the scientific literature in the last decade. Environmental factors that influence PROTOX inhibitors include temperature, irradiance and relative humidity. The most relevant physiological factors are the activity of enzymes that can detoxify herbicides and also of enzymes that mitigate the effects of oxidative stress in plants. The study also suggests some possible management strategies that could optimize the activity of PROTOX-inhibiting herbicides.

The objective of this study was to determine the activity of the enzyme acetolactate synthase in biotypes of wild poinsettia (Euphorbia heterophylla) with multiple resistance to ALS- and Protox- inhibitors in the presence and absence of imazapyr, imazethapyr and nicosulfuron. We conducted in vitro assay of ALS enzyme extracted from plants of Vitorino, Bom Sucesso do Sul and Medianeira biotypes (with multiple resistance) and a susceptible population in the absence and presence of imazapyr, imazethapyr and nicosulfuron. In the absence of herbicides, biotypes with multiple resistance showed higher affinity for the substrate of the enzyme compared with the susceptible population. The herbicides imazapyr, imazethapyr and nicosulfuron had little effect on the enzyme activity of ALS-resistant biotypes and, conversely, high inhibitory effect on ALS of the susceptible population. Resistance factors were very high, greater than 438, 963 and 474 for Vitorino, Bom Sucesso do Sul and Medianeira biotypes, respectively. The resistance to ALS inhibitors is due to the insensitivity of ALS to herbicides of both imidazolinone and sulfonylurea groups, characterizing a cross-resistance.

The existence of large areas infested with populations of Conyza spp. resistant to glyphosate in Brazil demands appropriate and integrated management strategies. This experiment aimed to identify soybean cultivars with greater competitive ability with horseweed plants and to determine plant characteristics associated with this ability. The experiment was arranged in a randomized complete block design with split plots. Seven soybean cultivars (CD 225 RR, BRS 232, CD 226 RR, NK 7054 RR, BMX Apollo RR, BRS 245 RR and BRS 255 RR) were allocated in the plots, and two interference situations (absence and 13.3 plants of Conyza m-2, transplanted seven days before soybean planting) in the subplots. The average yield loss due to competition with horseweed was 25%. Cultivar CD 226 RR showed no significant grain yield loss due to competition, compared to the control without infestation, but showed the lowest average grain yield. The BRS 232 genotype showed loss of grain yield of only 14%, and presented positive plant height and leaf mass at 20 DAE, as well as dry matter of stems+branches in all evaluations, features related to its higher performance and greater ability to withstand competition with horseweed plants.

The intensive use of pesticides have contaminated the soil and groundwater. The application of herbicides as controlled release formulations may reduce the environmental damage related to their use because it may optimize the efficiency of the active ingredient and reducing thus the recommended dose. The objective of this study was to evaluate the persistence of the herbicide atrazine applied as commercial formulation (COM) and as controlled release formulation (xerogel - XER) in Oxisol. The experimental design used was split-plot randomized-blocks with four replications, in a (2 x 6) + 1 arrangement. The two formulations (COM and XER) were assigned to main plots and different atrazine concentrations (0, 3.200, 3.600, 4.200, 5.400 and 8.000 g atrazine ha-1) were assigned to sub-plots. Persistence was determined by means of dissipation kinetics and bioavailability tests. The methodology of bioassays to assess the atrazine availability is efficient and enables to distinguish the tested formulations. The availability of atrazine XER is higher than the commercial in two different periods: up to 5 days after herbicide application and at the 35th day after application. The XER formulation tends to be more persistent in relation to COM formulation.

O conhecimento dos fatores que limitam o desempenho dos herbicidas permite selecionar os momentos mais apropriados para sua eficácia, otimizar a dose aplicada e reduzir o custo de produção. O objetivo desta revisão foi sintetizar o conhecimento do impacto das variáveis ambientais (temperatura do ar, umidade relativa do ar e luminosidade) na eficácia de herbicidas inibidores da ACCase. Temperatura do ar e umidade relativa do ar são as variáveis ambientais que mais alteram o desempenho desses herbicidas no controle das plantas daninhas. Em condições naturais, essas variáveis, juntamente com a luminosidade, interagem entre si - fato que dificulta a escolha do momento adequado para a aplicação do herbicida e a decisão do fator determinante na eficiência do produto. Sob condições controladas, é possível identificar a influência de cada um desses fatores. Aumento da umidade relativa do ar e da temperatura do ar, até certo limite, amplia a eficácia dos inibidores da ACCase no controle das plantas daninhas, pois favorece a absorção e a translocação do produto pela planta. Intensidade luminosa, quando em níveis elevados, também proporciona esses benefícios, porém há condições em que o sombreamento confere melhor desempenho aos herbicidas. A otimização da eficácia dos herbicidas inibidores da ACCase no controle das plantas daninhas passa por uma correta análise da influência de cada uma das variáveis ambientais supracitadasUnderstanding the factors that limit herbicide performance would allow selecting the appropriate time to spray the compounds, optimizing the dose applied, and reducing the production costs. The objective of this review was to synthesize the information available on the literature on the effect of the environmental conditions (air temperature, relative humidity, and irradiance) on the efficacy of the ACCase-inhibiting herbicides. Air temperature and relative humidity are the most important environmental variables altering the performance of these herbicides on weed control. Under natural conditions, these variables, along with irradiance, interact with one another, making it difficult to decide the best time to select herbicide application. Under controlled conditions, it is possible to identify the individual influence of each factor on herbicide efficacy. Increased relative humidity and air temperature increase the efficacy of ACCase-inhibitors to a certain extent, because of increased uptake and translocation of the herbicides by the plants. Light intensity, when increased, also provides these benefits, but sometimes shading provides better performance of these herbicides. To optimize the efficacy of ACCase-inhibitors on weed control, it is necessary to analyze the influence of each of the variables mentioned above.

Initialism is a new word proposed to indicate the "shade-avoidance syndrome". Plants detect the presence of neighbor plants very early in the growing season through changes in light quality. They modify the allocation of photosynthesis products privileging shoot growth over the roots. One of the hypotheses of the authors is that, when weed management is timely scheduled, a "blind" crop could be more productive because it would avoid an imbalance on the shoot:root ratio (S:R). Two strategies were developed to test this hypothesis: a) to use the classical Yoda's Law to screen several crops for insensitivity to S:R imbalance; b) to evaluate several growth regulators to control the plant responses to crowding. Experimental results confirm that both strategies can yield insensitive plants. The possibilities of the use of this knowledge are discussed.Inicialismo é uma palavra nova proposta para indicar a "síndrome de escape ao sombreamento". Plantas detectam a presença de outras plantas vizinhas muito cedo no seu ciclo de crescimento por meio das mudanças na qualidade da luz. Elas modificam a alocação de produtos da fotossíntese, privilegiando o crescimento de ramos sobre as raízes. Uma das hipóteses dos autores é que, quando o manejo de plantas daninhas é programado para ser realizado em pós-emergência, uma cultura "cega" poderia ser mais produtiva, porque se evitaria um desequilíbrio nas proporções entre parte aérea e raiz (PA:R). Duas estratégias foram desenvolvidas para testar essa hipótese: a) usar a lei de Yoda clássica para averiguar a insensibilidade de diversas culturas ao desequilíbrio PA:R; e b) avaliar vários reguladores de crescimento para controlar as respostas das plantas ao adensamento. Os resultados experimentais confirmam que ambas as estratégias podem produzir plantas insensíveis ao inicialismo. Neste estudo são discutidas as possibilidades de utilização desse conhecimento.

El intenso empleo de glifosato contribuyó a la difusión de malezas con tolerancia a este herbicida, incluyendo especies como Ipomoea nil, bejuco en Argentina, o corriola, o corda-de-viola en Brasil. A su vez, el uso intensivo de imadozolinonas en ciertas regiones de Argentina contribuyó a la aparición de biotipos resistentes a herbicidas que actúan inhibiendo la enzima ALS como Amaranthus quitensis, yuyo colorado o ataco, conocido como carurú en Brasil. En ese país, también, aumentó la difusión de malezas con resistencia a glifosato como en Euphorbia heterophylla, leiteiro o amendoim-bravo y en Lolium multiflorum, azevém. El objetivo de esta investigación fue evaluar el antagonismo o el sinergismo de todas las combinaciones posibles entre dos de los siguientes herbicidas: glifosato, imazetapir, clomazone y lactofen, en el control de las malezas mencionadas. Biotipos susceptibles para todos herbicidas fueran usados en la investigación. Plántulas de yuyo colorado juveniles con dos cm de altura y de las otras malezas mencionadas con siete cm, fueron tratadas con los siguientes herbicidas en g ha-1 i.a.: glifosato 108; imazetapir 10; clomazone 160 y lactofen 30, aplicados solos. Otros seis tratamientos fueron incluidos en todas las combinaciones posibles entre dos de los herbicidas y dosis mencionados. También se empleó un testigo sin tratar. El efecto de la combinación de los herbicidas dependió de la especie evaluada y también de los herbicidas utilizados. Se obtuvo sinergismo solamente para la mezcla glifosato más imazetapir en ataco. Clomazone fue el herbicida con más antagonismo, y lactofen tuvo efecto neutro en la mayoría de las mezclas. Las combinaciones son consideradas potencialmente útiles en el control de malezas tolerantes o resistentes a glifosato.The intense use of glyphosate in Argentina has increased the spread of weeds with tolerance to this herbicide, like Ipomoea nil. Cases of weed resistance to ALS inhibitors were documented in Argentina with Amaranthus quitensis. Likewise, in Brazil, it has increased weed resistance to glyphosate in weeds such as Lolium multiflorum and Euphorbia heterophylla. The objective of this research was to assess antagonism or synergism to control of the mentioned weeds for all possible combinations between two of the following herbicides: glyphosate, imazethapyr, clomazone, and lactofen. Biotypes susceptible to all herbicides were used in the research. Seedlings of A. hybridus with two cm and of the others with seven cm, were treated with the herbicides glyphosate, imazethapyr, clomazone and lactofen at 108, 10, 160 y 30 g ha-1 a.i. respectively, applied alone. Six additional treatments were included in all possible combinations between two of the herbicides and doses as described above. An untreated control was also used. A non-ionic adjuvant at a ratio of 0.2% was added to all treatments, except for the treatment of glyphosate alone and the untreated. The effect of the herbicide mixtures depended on the species tested and also on the herbicides used. Synergism was obtained only in the mixture glyphosate + imazethapyr. Clomazone resulted predominantly in antagonism, and lactofen had a neutral effect in most of the evaluated herbicide mixtures. Herbicide combinations are considered potentially useful in controlling weeds resistant or tolerant to glyphosate.

Três experimentos foram realizados para verificar se o local de aplicação de fomesafen, folhas ou solo, afeta a eficácia desse herbicida em biótipos de E. heterophylla resistente e suscetível a ele; e determinar quais estruturas da planta são mais importantes no processo de absorção desse herbicida. Nos dois primeiros experimentos, testaram-se curvas de dose-resposta de fomesafen em biótipos com e sem resistência a inibidores da PROTOX, em pré-emergência (primeiro experimento) e em pós-emergência (segundo experimento). No terceiro experimento, diferentes locais de deposição de fomesafen foram avaliados, por meio do método de vaso duplo, para verificar quais as estruturas das plantas de E. heterophylla mais importantes na absorção do herbicida. Os resultados, em geral, indicam menor eficiência de controle quando o fomesafen é aplicado na parte aérea das plantas de E. heterophylla resistentes a esse herbicida, em comparação às suscetíveis, e que as diferenças entre os biótipos foram menores na aplicação em pré-emergência. Detectou-se maior eficiência do herbicida fomesafen aplicado ao solo quando este foi colocado junto à parte aérea emergente das plantas suscetíveis e resistentes do que junto ao sistema de raízes destas. Esses resultados apóiam a hipótese de que diferenças foliares entre plantas resistentes e suscetíveis podem dificultar a absorção de fomesafen nos biótipos resistentes aos inibidores da PROTOX.Three trials were carried out to verify if the site of formesafen, absorption leaves or soil, affects the efficacy of controling this herbicide in wild poinsettia biotypes resistant and susceptible to the product; and to determine which plant structures are more important for fomesafen absorption. In the first two trials, fomesafen dose-response was evaluated on biotypes susceptible and resistant to PROTOX inhibitors, in the pre (first trial) and post emergence (second trial) applications. In a third trial, different deposition sites of fomesafen were evaluated using the double pot system to verify the structures of wild poinsettia plants which were most important to fomesafen absorption. Overall, the results indicated that shoot absorption of fomesafen was more limited on wild poinsettia biotypes with PROTOX resistance than on susceptible ones and that these differences between biotypes were less important when applied in pre-emergence. When applied to soil, fomesafen efficacy increased when the herbicide was placed near wild poinsettia shoots than close to their roots. These results support the hypothesis that leaf differences between resistant and susceptible plants may limit fomesafen absorption on biotypes resistant to PROTOX inhibitors.

Na agricultura atual, o método mais utilizado para o controle de plantas daninhas é o químico, em razão da facilidade de uso, elevada eficiência e baixa necessidade de mão de obra. No entanto, a utilização inadequada desses produtos provoca problemas ao ambiente e à saúde humana. Cresce, portanto, a busca por métodos alternativos de controle de plantas daninhas, menos demandadores de energia e menos tóxicos e agressivos ao ambiente. Este trabalho objetivou avaliar o efeito alelopático da cultura do girassol (Helianthus annuus) sobre diferentes espécies de plantas daninhas e cultivadas, em dois experimentos realizados em delineamento experimental completamente casualizado, utilizando o método da semeadura em substituição. O primeiro experimento foi realizado com quatro repetições, em esquema bifatorial. O primeiro fator foi constituído por seis espécies indicadoras: picão-preto (Bidens pilosa), corda-de-viola (Ipomoea grandifolia), caruru (Amaranthus hybridus), alface (Lactuca sativa, cultivar Aurélia), tomate (Lycopersicon esculentum, cultivar Santa Cruz), trigo (Triticum aestivum, cultivar BRS 208); e o segundo, pela presença ou não de plântulas de girassol. O segundo experimento foi composto por 24 tratamentos, representados por 23 genótipos de girassol e por uma testemunha sem girassol, utilizando-se quatro repetições. A espécie indicadora foi apenas o picão-preto. Em ambos os experimentos, no final do período de sete dias de convívio, foram avaliados o número de sementes germinadas e o comprimento radicular e da parte aérea das espécies indicadoras. Não foram observadas diferenças entre as porcentagens de germinação de quaisquer das espécies indicadoras avaliadas, em função da presença ou não das plântulas de girassol. A presença de plântulas de girassol estimulou o crescimento radicular das plântulas de tomate e trigo e inibiu o crescimento da parte aérea de picão-preto, trigo e corda-de-viola. Houve grande variabilidade de potencial alelopático entre genótipos de girassol sobre a germinação e o crescimento radicular e da parte aérea de Bidens pilosa. Os resultados demonstram que a técnica da semeadura em substituição é adequada para detectar efeitos estimulativos ou inibitórios de girassol sobre espécies indicadoras e para discriminar genótipos de girassol quanto à habilidade em inibir ou estimular plântulas de Bidens pilosa.In modern agriculture, the chemical method is the most used for weed control because it is highly efficient, easy to apply, and demands limited labor. However, the inadequate use of chemical products can lead to environmental and human health problems. Thus, there is a growing need to search for alternative weed control methods using substances which are less energy-demanding, less toxic and less aggressive to the environment. This work aimed to evaluate the allelopathic potential of sunflower (Helianthus annuus) culture on different weed and cultivated species, in two experiments conducted in a completely randomized design, using the relay seeding technique. The first experiment was carried out with four repetitions, in a bi-factorial scheme. The first factor was constituted by six indicative target species: beggarticks (Bidens spp.), common morninglory (Ipomoea grandifolia), pigweed (Amaranthus hybridus), lettuce (Lactuca sativa, cv. Aurélia), tomato (Solanum lycopersicum, cv. Santa Cruz), and wheat (Triticum aestivum, cv. BRS 208).The second factor was constituted by the presence or absence of sunflower seedlings. The relay seeding technique was applied. The second experiment was composed by 24 treatments including 23 sunflower genotypes and a control without sunflower, with four repetitions. The indicative species was only the beggarticks. In both experiments, at the end of seven coexistence days, number of germinated seeds, and root and aerial part length of the target species were evaluated. No difference was observed among the germination percentages of the indicative species evaluated in the presence or absence of the sunflower plants. The presence of the sunflower plants stimulated tomato and wheat root growth and inhibited the growth of the beggartick, wheat and common morninglory aerial parts. There was great variability of the potential allelopathic effect of the sunflower genotypes on germination and root and aerial part length of Bidens pilosa. The results show that the relay seeding technique is adapted to discriminate stimulating and inhibiting effects of sunflower among indicative species and to discriminate sunflower genotypes in their ability to inhibit or stimulate Bidens pilosa plants.

O objetivo do presente trabalho foi caracterizar o efeito alelopático do extrato aquoso de folhas de A. annua sobre a germinação de sementes e o desenvolvimento de plântulas de alface (Lactuca sativa L.) e leiteiro (Euphorbia heterophylla L.). O extrato aquoso bruto foi preparado a partir de 250 g folhas frescas extraídas em 1 L de água destilada. Este primeiro extrato foi filtrado e centrifugado, sendo utilizado o sobrenadante. Foram utilizadas as seguintes concentrações de 100% (extrato filtrado e centrifugado); 75%, 50% e 25% (diluições do extrato 100%); e 0% (água destilada). As sementes das espécies testadas foram distribuídas em placas de petri e acondicionadas em câmara de germinação. Foram analisadas as variáveis: germinabilidade (G), velocidade média de germinação (V), tempo médio de germinação (t), comprimento da radícula (CR) e massa seca das plântulas. A elevação da concentração do extrato aquoso de A. annua provocou redução na germinabilidade de alface e, a partir da concentração de 50%, a germinação foi completamente inibida. Para o leiteiro, a germinação foi totalmente inibida a partir da concentração de 75%. Observou-se também redução significativa na velocidade média de germinação de alface com a elevação da concentração do extrato, efeito que não foi observado para o leiteiro. O comprimento radicular do leiteiro foi significativamente reduzido nas concentrações de 25 e 50%, e totalmente inibido em 75 e 100%. Para alface, a concentração de 25% reduziu significativamente o comprimento radicular, e as concentrações de 50, 75 e 100% inibiram completamente a formação de raízes, mostrando ser esta espécie mais sensível que o leiteiro. Extratos aquosos de A. annua apresentaram ação alelopática inibitória sobre a germinação de sementes e o desenvolvimento de plântulas de alface e leiteiro.The aim of this work was to study the allelopathic effect of leaf aqueous extract of A. annua on seed germination and seedling development in lettuce (Lactuca sativa L.) and wild poinsettia (Euphorbia heterophylla L.). Crude aqueous extract was prepared from 250 g fresh leaves extracted in 1 L distilled water. This first extract was filtered and centrifuged and the supernatant was used. The following concentrations were employed of 100% (filtered and centrifuged extract), 75%, 50%, 25% (dilutions of the 100% extract) and 0% (distilled water). Seeds of the tested species were distributed in Petri dishes and placed into germination chambers. The analyzed variables were: germinability (G), germination mean velocity (V), germination mean time (t), radicle length (RL) and seedling dry matter. The increase in the concentration of A. annua aqueous extract reduced lettuce germinability and, from 50% concentration, germination was completely inhibited. For wild poinsettia, germination was completely inhibited from 75% concentration. There was a significant reduction in lettuce germination mean velocity with increasing extract concentrations, which was not observed for wild poinsettia. Radicle length in wild poinsettia significantly reduced at the concentrations 25 and 50% and was totally inhibited at 75 and 100%. As regards lettuce, 25% concentration significantly reduced radicle length, and the concentrations 50, 75 and 100% completely inhibited root formation, indicating this species is more sensitive than wild poinsettia. A. annua aqueous extracts presented inhibitory allelopathic action on seed germination and seedling development in lettuce and wild poinsettia.

Objetivou-se com este trabalho avaliar o efeito da integração de redução de espaçamento entre linhas sobre características morfofisiológicas de híbridos e estratégias de manejo químico de plantas daninhas em milho. O experimento foi realizado a campo, em delineamento de blocos casualizados, com quatro repetições, em um fatorial 2 x 2 x 5, em que o primeiro fator representou os híbridos de milho (Sprint, ciclo superprecoce e folhas mais eretas, e Penta, ciclo precoce e folhas mais planas); o segundo, espaçamentos entre linhas de milho (0,45 e 0,90 m); e o terceiro, tratamentos para controle de plantas daninhas: 1. atrazine + simazine (1.500 + 1.500 g i.a. ha-1) em pós-precoce; 2. atrazine + simazine (1.500 + 1.500 g i.a. ha-1), em pós-precoce, complementada por nicosulfuron + atrazine (20 + 750 g i.a. ha-1 ), em pós-tardia; 3. atrazine + simazine (750 + 750 g i.a. ha-1 ), em pós-precoce; 4. testemunha capinada; e 5. apenas nicosulfuron+atrazine (20 + 750 g i.a. ha-1 ), em pós -ardia. O espaçamento de 45 cm favoreceu a infestação de plantas daninhas na linha do milho, enquanto no espaçamento de 90 cm as maiores infestações foram observadas nas entrelinhas da cultura. As aplicações complementares de atrazine+nicosulfuron em pós-tardia foram importantes para controlar plantas daninhas no híbrido Sprint em espaçamento convencional, mas não necessárias para o híbrido Penta, nos espaçamentos utilizados. Observou-se no híbrido Penta que a redução do espaçamento afetou o rendimento de grãos, enquanto para Sprint não foi verificada redução de produtividade.This work was carried out to evaluate the effect of integrating morphophysiological characteristics of hybrids, row spacing reduction and chemical weed management in corn. The experiment was carried out under field conditions, in a randomized complete block design, in a 2 x 2 x 5 factorial scheme, with four replications, with the first factor consisting of corn hybrids (Sprint, too early-maturing and more erect leaves and Penta, early-maturing and more plane leaves),and the second consisting of row spacing (0.45 and 0.90 m) and the third, of the weed control treatments: 1.atrazine + simazine (1.500 + 1.500 g.a.i. ha-1 ) at early post-emergence; 2.atrazine + simazine (1.500 + 1.500 g a.i. ha-1), in early post-emergence, complemented by nicosulfuron+atrazine (20 + 750 g a.i. ha-1 ), at late post-emergence; 3.atrazine+simazine (750 + 750 g a.i. ha-1 ), at early post-emergence; 4.control with weeding; 5. only nicosulfuron+ atrazine (20 + 750 g a.i. ha-1 ), in late post-emergence. The 45 cm spacing favored weeds in the row while in the 90 cm spacing, the greatest weed infestations occurred in the interrows. Complementary applications of atrazine + nicosulfuron were needed to control weeds in the Spring hybrid and conventional row systems, but not to control Penta at the row width used. For the Penta hybrid, reduced spacing decreased corn grain yield, while for the Sprint hybrid, no corn grain yield reduction was observed.

Em geral, a eficiência de herbicidas inibidores da ACCase é reduzida quando da aplicação em conjunto com herbicidas latifolicidas. Dois experimentos - em casa de vegetação e campo - objetivaram determinar a existência de antagonismo nas associações de clodinafop-propargyl a metsulfuron-methyl ou 2,4-D, para controle de azevém anual. Em casa de vegetação, o delineamento foi o completamente casualizado, com 21 tratamentos compostos pela aplicação de clodinafop (0, 3, 6, 12, 24, 48 e 96 g ha-1) isolado ou em mistura com metsulfuron-methyl (2 e 4 g ha-1) ou 2,4-D (470 g ha-1). Em campo, o delineamento foi de blocos casualizados, com 12 tratamentos, arranjados em fatorial 6 x 2, composto pelos níveis de clodinafop-propargyl (0, 3, 6, 12, 24, 48 e 96 g ha¹) isolado ou em mistura com metsulfuron-methyl (2 g ha-1). A avaliação visual de controle, em casa de vegetação, revelou I50 das misturas de clodinafop-propargyl + metsulfuron-methyl (2 e 4 g ha-1) ou clodinafop-propargyl + 2,4-D (470 g ha-1), respectivamente, 33, 84 e 151% superiores ao de clodinafop-propargyl isolado. Já para matéria verde de azevém, o I50 das misturas supracitadas foi, respectivamente, 119, 244 e 72% superior ao de clodinafop-propargyl isolado. Em campo, ocorreu redução da matéria verde de azevém com a elevação dos níveis de clodinafop-propargyl isolado, mas não houve variação da matéria verde com a elevação dos níveis de clodinafop-propargyl, em associação a metsulfuron-methyl. Os resultados evidenciam a existência de antagonismo entre clodinafop-propargyl e os herbicidas metsulfuron-methyl e 2,4-D. São feitas considerações sobre as possíveis vantagens da aplicação dos herbicidas em mais de uma operação de controle, em comparação à associação entre graminicidas e latifolicidas.The efficacy of ACCase inhibitors is usually reduced when tank-mixed with broad leaf herbicides. A greenhouse and a field experiments were carried out to determine the existence of antagonistic effects of clodinafop-propargyl associated with metsulfuron methyl or 2,4-D to control Italian ryegrass (Lolium multiflorum). In the greenhouse experiment, 21 treatments were tested, composed by clodynafop(0, 3, 6, 12, 24, 48 and 96 g ha-1) alone or tank-mixed with metsulfuron (2 and 4 g ha-1) or 2,4-D (470 g ha-1). In the field experiment, twelve treatments were set up in a factorial 6 x 2, composed by clodinafop (0, 3, 6, 12, 24, 48 and 96 g ha-1) alone or tank-mixed with metsulfuron (2 g ha-1). In the greenhouse experiment, the control (visual evaluation), I50 from the mixtures with metsulfuron (2 and 4 g ha-1) or 2,4-D (470 g ha-1) were 33, 84 and 151% higher than clodinafop applied alone. The I50 from the rye live matter from the mixtures cited above were, respectively, 119, 244 and 72% higher than clodinafop applied alone. In the field experiment, rye live matter reduction was observed with increase of the levels of clodinafop applied alone, but rye live matter did not decrease, changing the levels of clodinafop tank-mixed with metsulfuron. The results reveal the antagonistic effect of tank-mixtures of clodinafop and metsulfuron or 2,4-D. We did make some considerations on the advantages of applying herbicides in more than one control operation, in comparison to graminicide and latifolicide mixtures.

A resistência de plantas daninhas aos herbicidas caracteriza-se como um fenômeno evolutivo, decorrente da seleção imposta por estes. Esse é um problema grave que vem aumentando nos últimos anos nas áreas agrícolas em todo o mundo. A prevenção por meio de métodos alternativos de manejo atrasa o aparecimento de plantas resistentes, porém o monitoramento periódico das lavouras é a melhor forma de evitar a disseminação quando do surgimento da resistência. Métodos diagnósticos rápidos, eficazes e precisos são úteis na confirmação dos casos de resistência, evitando a disseminação de sementes na área. Diversos métodos têm sido desenvolvidos nos últimos anos, buscando agilizar o diagnóstico da resistência. Recentemente, métodos desenvolvidos através do uso da biotecnologia têm sido aprimorados e mostram uma tendência para o futuro na detecção da resistência aos herbicidas pelas plantas daninhas. No presente trabalho, objetivou-se discutir os métodos para diagnóstico da resistência em plantas daninhas aos herbicidas relatados pela literatura, apresentando suas vantagens e desvantagens, bem como abordando suas possibilidades de aplicação.Weed resistance to herbicides is an evolutive phenomenon caused by the selection imposed by the herbicides. This serious problem has been increasing in the last years in agricultural areas. Prevention through alternative management methods delays the appearance of resistant weeds. However, periodic monitoring of farmlands is the best way to avoid the spreading of the selected resistance biotypes. Fast, efficient and precise diagnosis methods are useful in the confirmation of resistance cases avoiding seed dissemination. Different methods have been developed in the last years seeking to improve resistance diagnosis. Recent methods developed through biotechnology have been improved and are promising methods for herbicide resistant weed detection.

A metodologia de curvas de resposta e isobologramas, feitos a partir dos I50 gerados pelas curvas, tem sido bastante apregoada na comprovação de sinergismo. O experimento foi conduzido em casa de vegetação, com girassol cultivado em solução nutritiva (Hoagland), aplicando-se na solução 27 tratamentos, com os herbicidas metribuzin nas doses de 0, 70, 140, 280, 560 e 1.130 nM e clomazone nas doses de 0, 40, 80, 160, 320 e 640 mM. Combinaram-se as doses dos herbicidas de maneira a produzir os I50 das seis curvas resultantes das associações. Nas plantas coletadas, cinco dias após a aplicação, determinou-se o percentual de dano, a massa fresca e a massa seca das plantas de girassol. Os seis pontos de I50 de cada variável foram utilizados para formar isobologramas, onde os I50 dos herbicidas aplicados isolados, unidos por uma reta, formaram a isobole de aditividade. Em torno desta, foram traçadas faixas de confiança, a partir do produto dos intervalos de confiança dos I50 dos herbicidas isolados, dentro das quais se posicionaram os I50 resultantes das associações. Todas as associações situaram-se na região de sinergismo, abaixo da isobole de aditividade, embora com diferentes probabilidades. Na variável massa seca, a associação das doses de clomazone com 140 nM de metribuzin demonstrou probabilidade de, em torno de 90%, ser uma interação sinérgica.The Dose-Response Curve and Isobolograms methodology, based on the I50 generated by curves has been largely recommended to demonstrate synergism. The experiment was conducted in a greenhouse, with sunflower cultivated in nutrient solution (Hoagland), applying in solution 27 treatments, with the herbicides metribuzin, at the rates of 0, 70, 140, 280, 560 and 1,130 nM and clomazone, at the rates of 0, 40, 80, 160, 320 and 640 mM. The herbicide doses were combined so as to produce the I50 of six resulting curves from the matches. Injury percentage, and fresh and dry weight of sunflower plants were determined five days after application on the collected plants.The six points of I50 from each variable were used to obtain isobolograms, where the I50 of herbicides applied alone, jointed by a straight line, formed the isobole of additivity. Around of it, confidences strips were drawn from the product of confidences intervals of isolated herbicides I50's, where were positioned the I50 resulting from the mixtures. All the I50 mixtures were positioned in the synergism zone, below the isobole of additivity, although with different probabilities. For dry mass variable, the mixture of clomazone rates with 140 nM of metribuzin showed probability around 90% of being a synergistic interaction.

Populações de Euphorbia heterophylla resistentes (R) aos herbicidas inibidores da enzima acetolactato sintase encontram-se amplamente disseminadas em várias regiões do Brasil. Resíduos culturais de várias espécies apresentam elevado potencial para suprimir o desenvolvimento de plantas daninhas. O objetivo deste trabalho foi avaliar os efeitos de diferentes níveis de resíduos das partes aéreas de sorgo, milho e aveia na supressão de E. heterophylla resistente a herbicidas. Foram realizados dois experimentos em vasos com delineamento experimental completamente casualizado, com quatro repetições. No primeiro, os tratamentos foram arranjados em fatorial 4x6, em que o fator A representou três híbridos de sorgo (AG-2501, Dow 1P-400 e BR-501) e um de milho (AG-3010); e o fator B, seis níveis de resíduos na superfície do solo (0, 3,25, 6,5, 9,75, 13 e 26 t ha-1). Os tratamentos do segundo experimento foram arranjados em fatorial 2 x 6, em que A representou as espécies (sorgo e aveia) e B os níveis de resíduos (0, 1,12, 3,25, 6,5, 13 e 26 t ha-1). A emergência das plantas de E. heterophylla foi atrasada e reduzida. Estimou-se que seriam necessárias 28,6 t ha-1 de palha de sorgo para causar redução de 50% na emergência de plântulas. O número de folhas diminuiu com a elevação dos níveis de resíduos da parte aérea de sorgo e milho. Níveis intermediários de resíduos de Dow 1P-400 reduziram mais o IVE do que os outros híbridos de sorgo, entretanto não houve diferenças entre genótipos quanto à emergência de plântulas. Resíduos da parte aérea de aveia não foram eficazes em reduzir a emergência de E. heterophylla.Euphorbia heterophylla populations resistant to ALS-inhibitors were reported in many regions in Brazil. Straw residues of many species have shown high potential to supress weeds. The objective of this work was to evaluate the efficacy of different rates of sorghum, corn and black oat shoot residues in supressing emergence and growth of E. heterophylla resistant to herbicides. Two experiments were conducted in pots in a completely randomized design, with four replicates, arranged in a factorial scheme. In the first trial, factor A was composed by sorghum (AG-2501, Dow 1P-400 and Br-501) and corn (AG-3010) hybrids and factor B by six rates of sorghum and corn residues above soil surface (0, 3.25, 6.5, 9.75, 13 and 26 t ha-1 ). In the second trial, factor A was composed by two species (sorghum and oat) and factor B by shoot residue rates (0, 1.12, 3.25, 6.5, 13 and 26 t ha-1). Emergence of E. heterophylla plants was delayed and decreased. The total number of leaves decreased with increase of sorghum and corn straw rate. However, it was estimated that 28.6 t ha-1 of sorghum residues would be necessary to decrease 50% emergence. Dow 1P-400 sorghum straw at intermediate rates presented a greater potential to decrease IVE than the other sorghum hybrids, but no difference was observed between emergence of sorghum genotypes. Black oat shoot straw was not efficient in decreasing E. heterophylla emergence.

Quatro bioensaios, dois em casa de vegetação e dois em laboratório, foram conduzidos com o objetivo de identificar biótipos de Euphorbia heterophylla (EPHHL) com resistência múltipla a inibidores da ALS e da PROTOX. Em casa de vegetação, plantas do biótipo suscetível (S) e dos biótipos 4 e 23, suspeitos de resistência múltipla, foram aspergidas com diferentes doses de imazethapyr e fomesafen. Nos bioensaios em laboratório, sementes dos biótipos S e 4 foram depositadas em placas de Petri contendo diferentes concentrações dos mesmos herbicidas. Curvas de dose-resposta foram ajustadas, utilizando os modelos logístico e polinomial, respectivamente, para os dados obtidos em casa de vegetação e em laboratório. Em casa de vegetação, o fator de resistência (FR) a imazethapyr para o biótipo 4 foi superior a 24, enquanto para o biótipo 23 ele foi de 15. Os FRs a fomesafen foram, respectivamente, de 62 e 39, para os mesmos biótipos. Em um período de 144 horas, concentrações de imazethapyr e fomesafen no bioensaio em laboratório foram capazes de discriminar os crescimentos da parte aérea e radicular dos biótipos de EPHHL com resistência múltipla e S. Os resultados confirmam ser tanto os testes em casa de vegetação quanto os laboratoriais, utilizando placas de Petri, metodologias apropriadas para discriminar biótipos de EPHHL S daqueles com resistência múltipla.Four bioassays were developed under greenhouse and laboratory conditions to identify Euphorbia heterophylla (EPHHL) biotypes with multiple resistance to PROTOX and ALS-inhibiting herbicides. In the greenhouse bioassays, plants of a susceptible (S) biotype and of two biotypes suspected of multiple resistance (#4 and #23) were sprayed using different levels of the herbicides imazethapyr and fomesafen. The laboratory bioassays consisted of a comparative test between biotypes S and #4, exposed to germination in imazethapyr and fomesafen solutions. Dose-response relationships were adjusted using logistic and polynomial models, respectively, for data obtained from greenhouse and laboratory bioassays. For biotype #4, the resistance factor (RF) to imazethapyr was above 24, while for biotype #23 it was 15. FR to fomesafen were, respectively, 62 and 39, for the same biotypes. In the laboratory bioassay, a period of 144 hours was sufficient to discriminate differencial growth response to imazethapyr and fomesafen levels between R and S biotypes. The results confirm that both greenhouse and laboratory tests with Petri dishes are appropriate methodologies to discriminate S and multiple R EPHHL biotypes.

Determinações bioquímicas e físico-químicas são úteis para verificar o tipo de interação herbicida. Três experimentos foram conduzidos com dois herbicidas geradores de estresse oxidativo para demonstrar o possível sinergismo em sua associação. Plantas de girassol foram cultivadas em solução nutritiva até o estádio de dois pares de folhas, quando então os herbicidas foram aplicados. Os tratamentos consistiram de metribuzin a 0 e 0,28 µmol L-1 e clomazone a 0 e 80 µmol L-1, com quatro repetições, isolados e em mistura. No material coletado, três dias após a aplicação, determinou-se o malondialdeído (MDA), pelo método das substâncias reativas ao ácido tiobarbitúrico (TBARS). Em outro experimento, os herbicidas foram testados sobre 40 discos de 4 mm de folhas de girassol imersas em 5 mL de tampão MES-NaOH, em pH 6,5. Os tratamentos consistiram de metribuzin a 0 e 12 µmol L-1 e clomazone a 0 e 237 µmol L¹, com quatro repetições, isolados e em mistura. Os discos foliares tratados foram incubados por 24 h no escuro a 24 ºC e por 36 h sob luz, à mesma temperatura. A condutividade eletrolítica da solução foi então medida. Em relação ao metribuzin e clomazone aplicados isoladamente, a mistura dos dois herbicidas aumentou o equivalente MDA em 217 e 166%, e a condutividade eletrolítica, em 37 e 41%, respectivamente. Esses resultados demonstram, em nível bioquímico e físico-químico, a existência de sinergismo na mistura de metribuzin e clomazone, nas doses estudadas.Biochemical and physical-chemical determinations can help verify the type of herbicide interaction. Three experiments were conducted with two oxidative stress generating herbicides to demonstrate possible synergism in their association. Sunflower plants were grown in nutrient solution up to the stage of two pairs of leaves, followed by herbicide application. Treatments consisted of metribuzin at 0 and 0.28 µmol L-1 and clomazone at 0 and 80 µmol L-1, in four replicates, alone and in combination. In the material collected, three days after application, malondialdehyde content was determined by the TBARS method. In another experiment, the herbicides were tested over forty 4 mm sunflower leaf discs in 5 mL of MESNaOH pH 6.5 buffer. Treatments consisted of metribuzin at 0 and 12 µmol L-1 and clomazone at 0 and 237 µmol L-1, in four replicates, alone and in combination. The treated leaf discs were dark-incubated for 24 h at 24 °C and light-incubated for 36 h at the same temperature. Electrolyte leakage of the solution was then measured. Compared to application of metribuzin and clomazone alone the two herbicide combination increased the MDA equivalent in 217% and 166%, and electrolyte leakage in 37 and 41%, respectively. These results demonstrate the existence of synergism in the metribuzin/clomazone combination at the studied rates, at a biochemical and physical-chemical level.

Dentre as causas da ineficácia no controle de plantas daninhas destaca-se a resistência delas aos herbicidas. Os objetivos deste trabalho foram avaliar a suspeita de resistência de Eleusine indica a inibidores de acetil-CoA carboxilase (ACCase) e investigar a ocorrência de resistência cruzada entre os inibidores de ACCase. Biótipo de Eleusine indica originado do Mato Grosso com suspeita de resistência aos herbicidas inibidores de ACCase foi avaliado em casa de vegetação na sua suscetibilidade para diversos produtos do grupo dos ariloxifenoxipropionatos e cicloexanodionas. Estudos de resposta à dose confirmaram que o biótipo era 18 vezes mais insensível ao sethoxydim do que biótipo suscetível nunca aspergido com herbicidas. Também se constatou resistência cruzada ao fenoxaprop, cyhalofop, propaquizafop e butroxydim. Não se observou resistência cruzada aos produtos fluazifop, haloxyfop, quizalofop e clethodim.Among the causes for weed control inefficacy, the worst one is resistance to herbicides. The objectives of this work were to evaluate an Eleusine indica biotype suspected of resistance to ACCase inhibitors and to investigate the occurrence of cross- resistance to several ACCase inhibitors. One biotype of Eleusine indica originated from Mato Grosso with suspected resistance to ACCase inhibitors was evaluated in a greenhouse in relation to its susceptibility to several products of the ariloxyphenoxypropionate and cyclohexanedione groups. Studies on dose response confirmed that the suspected biotype was 18 times more insensitive to sethoxydim than the susceptible biotype that had never been treated with herbicides. Cross-resistance was confirmed for fenoxaprop, cyhalofop, propaquizafop and butroxydim. No cross-resistance was observed with fluazifop, haloxyfop, quizalofop, and clethodim.

Este trabalho constou de dois ensaios que avaliaram a toxicidade ao milho e a eficácia de controle de plantas daninhas dos herbicidas atrazine, da mistura foramsulfuron + iodosulfuron e do inseticida clorpirifós, isoladamente ou em mistura, aplicados em pósemergência. Utilizou-se o delineamento de blocos ao acaso com quatro repetições. No primeiro ensaio, todos os tratamentos foram capinados e constaram de: atrazine (3.000 g ha¹ de i.a.); atrazine + clorpirifós (3.000 + 225 g ha-1 de i.a.); atrazine + foramsulfuron + iodosulfuron + clorpirifós (2.250 + 15 + 1 + 225; 1.500 + 22,5 + 1,5 + 225; e 750 + 30 + 2 + 225 g ha-1 de i.a.); foramsulfuron + iodosulfuron (45 + 3 g ha-1 de i.a.); foramsulfuron + iodosulfuron + clorpirifós (45 + 3 + 225 g ha-1 de i.a.); e testemunha sem aplicação de herbicidas. Já no segundo ensaio foram utilizados todos os tratamentos anteriores, com exceção da mistura de todos os produtos nas doses de 750 + 30 + 2 + 225 g ha-1 de i.a., além dos respectivos tratamentos sem capina. Utilizou-se o cultivar de milho AG 3010 (híbrido duplo, superprecoce, tolerante a inibidores da ALS). Em 2002/2003, avaliou-se a toxicidade a milho e o rendimento, enquanto em 2003/2004 também foi avaliada a eficácia de controle de plantas daninhas. O uso de atrazine isoladamente ou em mistura com clorpirifós não gerou toxicidade às plantas de milho. A adição de clorpirifós à mistura foramsulfuron + iodosulfuron acentuou a injúria ao milho. A inclusão de atrazine simultaneamente à redução dos níveis de foramsulfuron + iodosulfuron permitiu reduzir em parte a injúria a plantas de milho, mantendo o controle de BRAPL e ampliando os níveis de controle de EPHHL.Two trials evaluated corn toxicity and weed control efficacy of the herbicides atrazine, foramsulfuron, and iodosulfuron and the insecticide chlorpyriphos applied at postemergence alone or in mixture. A randomized complete block design was used with four replications. In the first trial, the treatments (weed free throughout cultivation) were: atrazine (3000g ha-1 of a.i.); atrazine + clorpyriphos (3000 + 225g ha-1 of a.i.), atrazine + foramsulfuron + iodosulfuron + chlorpyriphos (2,250 + 15 + 1+ 225; 1,500 + 22.5 + 1.5 + 225 and 750 + 30 + 2 + 225 g ha-1 of a.i.); foramsulfuron+ iodosulfuron (45 + 3 g ha-1 of a.i.); foramsulfuron + iodosulfuron + chlorpyriphos (45 + 3 + 225 g ha¹ of a.i.), and a check without herbicides. In the second trial, the same treatments were used, except for atrazine + foramsulfuron + iodosulfuron + chlorpyriphos (750 + 30 + 2 + 225 g ha-1 of a.i.), besides the same treatments above without weed cultivation. AG 3010 cultivar, a short-cycle double hybrid, tolerant to ALS herbicides, was used. During the 2002/2003 agricultural season, corn toxicity and grain yield were evaluated, while during 2003/2004 ,weed control efficacy was also evaluated. Atrazine alone or mixed with chlorpyriphos did not cause any toxicity to the corn plants. Chlorpiryphos + foramsulfuron and iodosulfuron association can increase corn plant injury. The inclusion of atrazine concomitant to foramsulfuron and iodosulfuron reduction allowed partial reduction of corn plant injury, maintaining BRAPL control and enhancing the level of EPHHL control.

Herbicidas inibidores da enzima acetolactato sintase (ALS) têm sido amplamente utilizados no controle da planta daninha picão-preto (Bidens pilosa). A pressão de seleção causada pelo uso intensivo desses herbicidas tem selecionado biótipos de picão-preto resistentes. O objetivo deste trabalho foi avaliar o grau de similaridade genética entre acessos de picão-preto resistentes aos herbicidas inibidores da ALS, bem como a relação entre coeficiente de similaridade genética e distância geográfica desses acessos. Para isso, sementes de dois grupos de acessos de picão-preto, originárias de uma propriedade em Pato Branco, Paraná, resistentes aos herbicidas inibidores da ALS foram colhidas, e plântulas foram cultivadas em casa de vegetação na Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre-RS, em outubro de 2004. Por meio do marcador molecular RAPD (polimorfismo de DNA amplificado ao acaso) foi possível avaliar a similaridade genética entre os acessos de picão-preto. Na análise conjunta dos acessos, dos 20 primers utilizados, 17 apresentaram-se polimórficos, amplificando um total de 94 bandas. Houve baixa similaridade genética (38%) entre acessos de picão-preto resistentes aos herbicidas inibidores da ALS originários de uma mesma propriedade. Não foi observada relação entre distância genética e distância geográfica entre os acessos avaliados.Acetolactate synthase (ALS)-inhibiting herbicides have been widely used to control the weed hairy beggarticks (Bidens pilosa). The selection pressure caused by intensive herbicide use has selected hairy beggarticks resistant biotypes. The objectives of this work were to evaluate the degree of genetic similarity among hairy beggarticks accesses (Bidens pilosa) resistant to ALS-inhibiting herbicides, and to evaluate the relation between genetic similarity and geographic distance. Seeds of two groups of hairy beggarticks accesses resistant to ALS-inhibitors were sampled from a farm at Pato Branco, Paraná, and seedlings were grown in the greenhouse at the Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, in Ocober/2004. The use of RAPD (Random Amplified Polymorphic DNA) molecular markers allowed evaluating the genetic similarity among hairy beggarticks accesses. In the analysis of both access groups, out of twenty primers assessed, only seventeen displayed polymorphism and amplified a total of 94 bands. There is low genetic similarity (38%) among hairy beggarticks accesses resistant to ALS inhibitors from the same farm. There is no relationship between genetic distance and geographic distance in the evaluated accesses.

Herbicide resistance was reported in Brazil almost ten years ago. One of the main weeds with herbicide resistance is wild poinsettia (Euphorbia heterophylla). This work evaluates the distribution of ALS-resistant E. heterophylla in two states in southern Brazil and determines the major contributing management causes for weed resistance selection in the area. E. heterophylla seeds from 148 sites located in Paraná and Rio Grande do Sul were sampled during 2001 and 2002. Farmers provided specific site data for weed control, tillage system, crop rotation and harvesting operations during previous years. ALS resistant E. heterophylla biotypes were found widely distributed in the survey area. Data analysis suggests seed dissemination is unlikely to explain the widespread distribution of resistance. The most probable factor for the selection of the resistant E. heterophylla is the persistent high use of ALS-inhibiting herbicides over time. Indirect evidence is presented demonstrating the need to educate legislators and farmers about the importance of herbicide mixtures as a strategy to prevent herbicide resistance.A resistência aos herbicidas foi relatada no Brasil há quase uma década. Uma das principais plantas daninhas com resistência aos herbicidas é a leiteira (Euphorbia heterophylla). Este trabalho foi planejado para avaliar a distribuição geográfica de E. heterophylla resistente aos herbicidas nos estados do Paraná e Rio Grande do Sul e para obter dados que identificassem os principais fatores de manejo associados à seleção de biótipos resistentes na área. Sementes de E. heterophylla de 148 locais foram coletadas nos anos de 2001 e 2002. Em cada local, os agricultores informaram os procedimentos relativos a controle de plantas daninhas, sistema de preparo do solo, rotação de culturas e colheita. Este trabalho demonstrou que biótipos resistentes aos herbicidas inibidores da ALS estão amplamente distribuídos na região amostrada. A disseminação de sementes de plantas resistentes não é a provável causa da ampla distribuição da resistência. O principal fator responsável pela seleção de plantas resistentes na espécie E. heterophylla foi a elevada utilização de herbicidas inibidores de ALS nos anos que antecederam a coleta. Foram apresentadas evidências indiretas que demonstram a necessidade de educar os legisladores e agricultores com respeito à importância da mistura de herbicidas na prevenção da resistência aos herbicidas.

A supressão da infestação de plantas daninhas por espécies cultivadas como culturas de cobertura pode ocorrer durante o desenvolvimento vegetativo das espécies cultivadas como cultura de cobertura, nos estádios precoces de desenvolvimento, ou após a sua dessecação. Efeitos de competição e alelopáticos exercidos durante a coexistência das plantas de cobertura com as espécies daninhas podem ser responsáveis pelo efeito supressivo. Dois experimentos foram realizados a campo, em 1999/2000 e 2000/2001, na área experimental da Faculdade de Agronomia da UFRGS, em delineamento experimental de blocos ao acaso com quatro repetições, objetivando determinar os efeitos de plantas vegetando de genótipos de sorgo, com capacidade distinta de produção de extratos radiculares hidrofóbicos, sobre a supressão de plantas daninhas. Em 1999/2000, os tratamentos foram constituídos pelos genótipos de sorgo RS 11, BR 601 e BR 304, representantes de três classes de produção de extratos radiculares hidrofóbicos em laboratório, pelo genótipo de milheto Comum RS e por uma testemunha sem culturas. Em 2000/2001, os tratamentos foram resultantes da combinação do fator genótipo e do fator posição das plantas daninhas (linha ou entrelinha das culturas). Nos dois anos experimentais, a densidade e o crescimento de plantas daninhas (SIDRH, BIDSS e BRAPL) foram semelhantes entre os genótipos de sorgo e entre estes e o do milheto. Isso ocorreu independentemente do local avaliado, na área total ou individualmente nas linhas e entrelinhas das culturas, indicando ausência de efeito supressor de exudatos hidrofóbicos a campo. No primeiro ano, aos 30 dias após a semeadura, reduções de 41% de infestação e de 74% de massa seca total de plantas daninhas foram observadas, comparando-se os tratamentos cobertos com culturas à testemunha sem culturas, enquanto no segundo ano, aos 14 dias após a semeadura, não foram observadas diferenças entre a área onde havia plantas de sorgo ou milheto e a testemunha descoberta. A densidade de plantas daninhas nas linhas foi inversamente proporcional à população de plantas vivas de sorgo nesse local.The capacity of supression of weed infestation by cultivation of cover crops can occur during the vegetative growth of the species cultivated as cover crops, at the early stages of development, or after their desiccation. Competition and allelopathic effects performed, during the coexistence of the cover crop with the weeds can be responsible for the supressive effect. Two experiments were carried out under field conditions, in 1999/2000 and 2000/2001, at the Experimental Station of Agronomy College, at the Federal University of Rio Grande do Sul (UFRGS), Brazil, in a randomized block design with four replications, to determine the effects of living plants of sorghum genotypes with distinct capacity of production of hydrophobic root extracts, on supressing weeds. In 1999/2000, the treatments consisted of the RS 11, BR 601, and BR 304 sorghum genotypes, representative of three classes of hydrophobic root extracts production in laboratory, Comum RS pearl millet genotype and a check without crops. In 2000/2001, the treatments were the result of combinations of genotype factors and weed position ( rows or interrows). In the two experimental years, the density and growth of weeds (SIDRH, BIDSS, and BRAPL) were similar between sorghum genotypes and of these with pearl millet. This occurred regardless of the place evaluated, in the total area or individually in the rows or interrows, indicating lack of suppressive effect of hydrophobic exsudates under field conditions. In the first trial, thirty days after seeding, reduction of 41% of infestation and 74% of weed total dry mass were observed, while in the second trial, 14 days after seeding, no differences were observed between sorghum and pearl millet areas and the check without cover crops. Weed density in rows was inversely proportional to living sorghum plant population in these places.

A capacidade de supressão de plantas daninhas por culturas de cobertura é bastante conhecida e explorada, embora seja pouco pesquisada a importância relativa dos efeitos físicos e alelopáticos sobre esse fenômeno. Dois experimentos foram realizados a campo, em 1999/2000 e 2000/2001, na área experimental da Faculdade de Agronomia da UFRGS, no delineamento experimental em blocos ao acaso, com quatro repetições, objetivando determinar os efeitos da cobertura morta de plantas de sorgo e de milheto sobre a supressão de plantas daninhas. Nos dois anos de condução dos experimentos, os tratamentos resultaram de um fatorial, em que o fator A foi constituído pelos genótipos de sorgo RS 11, BR 601 e BR 304, representantes de três classes de produção de extratos radiculares hidrofóbicos em laboratório, pelo genótipo de milheto Comum RS e por uma testemunha sem culturas; e o fator B, constituído por níveis de palha de cada genótipo sobre o solo. Em 1999/2000, níveis de palha de sorgo de 1,3 t ha-1 foram suficientes para reduzir 50% das infestações de Brachiaria plantaginea (BRAPL) e Sida rhombifolia (SIDRH). Em 2000/2001, 4 t ha-1 de palha de sorgo ou milheto foram suficientes para reduzir 91, 96 e 59% da população total de SIDRH, BRAPL e Bidens pilosa, respectivamente. A presença de resíduos da parte aérea de sorgo é mais importante na supressão de plantas daninhas do que a presença de resíduos das raízes dessa cultura.The weed supression capacity of cover crops is well known and explored, although only a few works have been conducted on the relative importance of the physical and allelopathic effects on this phenomenon. Two trials were carried out in the field, in 1999/2000 and 2000/2001, at the experimental area of the University of Rio Grande do Sul, Brazil, arranged in a randomized experimental block design with four replications to evaluate the effects of sorghum and pearl millet mulch on weedsupression. In both experimental years, the treatments resulted in a factorial, where factor A was composed by sorghum genotypes RS 11, BR 601, and BR 304, representatives of three classes of hydrophobic root extract production in the laboratory; the pearl millet genotype Comum RS; and by a check without cultures. Factor B was formed by different levels of straw of each genotype over the soil. In 1999/2000, sorghum straw levels of 1.3 t ha-1 were sufficient to decrease Brachiaria plantaginea (BRAPL) and Sida rhombifolia (SIDRH) infestations by 50%. In 2000/2001, 4 t ha-1 of sorghum or pearl millet straw were sufficient to decrease 91, 96, and 59% of the total SIDRH, BRAPL, and Bidens pilosa population, respectively. The presence of sorghum shoot residues is more important in weed supression than the presence of root residues of this crop.

Foram conduzidos dois experimentos em condições de casa de vegetação, com o objetivo de analisar comparativamente o crescimento de três biótipos de leiteira (Euphorbia heterophylla - EPHHL) resistentes (R) (Passo Fundo, Não-Me-Toque e Rio Pardo) e um suscetível (S) (Porto Alegre) aos herbicidas inibidores da ALS, por meio do cálculo da taxa de crescimento relativo (TCR) e dos índices que a compõem. Utilizou-se o delineamento experimental completamente casualizado, com três repetições e tratamentos organizados em fatorial 2 x 4 x 4, em que o fator A correspondeu às duas estações de crescimento (outono e primavera), o fator B aos quatro biótipos de EPHHL e o fator C às quatro épocas de determinação dos índices de crescimento das plantas de leiteira - no primeiro experimento, aos 15, 25, 35 e 45, e, no segundo, aos 23, 33, 43 e 53 dias após a emergência (DAE). No experimento realizado no outono não houve interação entre época de avaliação e biótipo nem efeito simples de biótipo. No experimento realizado na primavera, a razão de peso foliar (RPF) do biótipo de Não-Me-Toque foi superior em média à dos demais biótipos; a razão de área foliar (RAF) foi superior no biótipo de Não-Me-Toque aos 23 e 53 DAE; e não houve diferenças da TAL e TCR entre os biótipos. Esses resultados sugerem produtividade semelhante entre os biótipos R e S e, portanto, sua equivalência competitiva.Two trials were carried out under greenhouse conditions to compare the development of three ALS inhibitor herbicides resistant (R) wild poinsettia (Euphorbia heterophylla) biotypes (Passo Fundo, Não-Me-Toque and Rio Pardo - RS - Brazil) and one susceptible (S) (Porto Alegre - RS - Brazil) using relative growth rate (RGR) and related indices. The experiment was arranged as a completely randomized design, with three replications, in a 2 x 4 x 4 factorial, where factor A was two growth seasons (fall and spring); factor B, four biotypes of wild poinsettia, and factor C, four assessments of growth indices (first trial at 15, 25, 35 and 45 days after emergence (d.a.e.) and second trial at 23, 33, 43 and 53 d.a.e.). The fall trial showed no interaction between assessment and biotype nor simple biotype effect. The spring trial relative leaf weight (RLW) of Não-Me-Toque biotype was higher than that of the others; leaf area ratio (LAR) of Não-Me-Toque biotype was higher than 23 and 53 d.a.e.; there was no difference of RGR and net assimilation rate (NAR) among biotypes. These results indicate similar R and S biotype productivities and, therefore, their competitive equivalency.

ABSTRACT: Increased use of glyphosate in transgenic soybean areas has selected resistant and tolerant weed species. The aim of this study was to evaluate chemical management strategies for controlling Borreria latifolia and Richardia brasiliensis at pre-emergence (Pre), early post-emergence (Poste) and late post-emergence (Postl). Six experiments were carried out in a completely randomized design with four replicates per treatment in the Pre experiments and three in the Poste and Postl experiments, for each of the species. In the Pre experiments, tests were performed with herbicides imazethapyr, sulfentrazone, chlorimuron, diclosulam, S-metolachlor and saflufenacil. In the Poste experiments, seedlings were sprayed with herbicides bentazon, fomesafen, lactofen, flumioxazin and glyphosate. In Postl experiments, adult plants received glyphosate application associated with herbicides 2,4-D, carfentrazone, imazethapyr, flumiclorac, flumioxazin, sulfentrazone, chlorimuron, saflufenacil and glufosinate, plus three sequential applications with glyphosate only and paraquat/diuron. In the experiments, there was a control treatment without application of herbicides. In the Pre experiments, the plants established at 14 and 28 days after application (DAA) were evaluated. In the Poste and Postl experiments, shoot dry matter evaluation and visual control were performed at 14 and 28 DAA. The herbicides sulfentrazone, S-metolachlor and saflufenacil suppressed the emergence of both B. latifolia as R. brasiliensis; chlorimuron-ethyl and diclosulam were effective only on R. brasiliensis. In Poste, fomesafen, lactofen and flumioxazin reached levels of control over 90% of plants of both species. In Postl, glyphosate associated with carfentrazone, flumiclorac, flumioxazin, chlorimuron-ethyl, saflufenacil, glufosinate, and sequential applications of glyphosate/glyphosate, glyphosate/paraquat+diuron, glyphosate+2,4-D/paraquat+diuron reached levels control higher than 95%.