Herbicides in the initial growth and chlorophyll indices of sugarcane in pre-sprouted seedlings.

The aim of the present study was to assess the selectivity of herbicides applied in the pre and post-planting of pre-sprouted seedlings (PSS). The experiment was conducted in a greenhouse, using a completely randomized design, with nine treatments and four repetitions. The IACSP95-5000 cultivar was used. The treatments consisted of herbicides applied in five doses as follows: in pre-planting: sulfentrazone, diclosulam, imazapic, and imazapyr, in post-planting: ethoxysulfuron, halosulfuron, 2,4-D and MSMA, and a control treatment without herbicide. Injury symptoms were assessed at 7, 15, 30, 45, 60, 75, and 90 days after application (DAA), height, diameter, number of tillers, chlorophyll A, B, and total chlorophyll at 30, 60, and 90 DAA, leaf area, shoot and root dry mass at 90 DAA. The post-emergent herbicides were considered selective. Pre-planting herbicides reduced the variables assessed at 90 DAA, observed by linear regression for diclosulam and imazapic, and exponential regression for imazapyr. Treatments with sulfentrazone caused few injury symptoms, with subsequent recovery. In addition, all the variables analyzed were equal to control, with the sulfentrazone considered selective for the IACSP95-5000 cultivar.

Glyphosate-resistant hairy fleabane (Conyza bonariensis) exhibits a larger number of trichomes and altered stomatal density relative to the susceptible counterpart

Following the adoption of Roundup Ready crops, glyphosate spraying frequency increased, while the use of other herbicide modes of action was neglected. Herbicide-resistant biotypes were reported in three major Conyza species in Brazil, including Conyza bonariensis, increasing growers' bottom line. Considering that leaf surface structures affect proper herbicide deposition, uptake, and performance, this study aimed to characterize epicuticular surface components in glyphosate-resistant (R) and -susceptible (S) C. bonariensis. Conyza spp. seeds were collected in 36 locations in Brazil, and plants were subjected to resistance screening tests by spraying glyphosate at 720 and 1440 g ae ha-1 (0.5X and 1X the label recommended rate, respectively). For resistance level characterization, C. bonariensis biotypes with contrasting responses were selected for glyphosate dose-response assays. Leaf tissues for epicuticular surface analysis were harvested from newly-obtained R and S biotypes at two growth stages. Histological cuts were made on a leaf area of 25 mm² with a blade. Samples were fixed in Karnowsky solution, gradually changed to 100% ethanol, critical-point dried with CO2, and coated with gold, followed by stomatal and trichome density quantification using scanning electron microscopy. Results indicated a poor control with glyphosate in 33 of 36 Conyza spp. biotypes, and a high (31.5) resistance factor was calculated after dose-response trials. Leaf surface analysis indicated that C. bonariensis leaves are amphistomatic and exhibit tectorial trichomes. A higher number of trichomes and altered stomatal density (number.mm²) were quantified in R compared to the S counterpart, potentially reducing glyphosate uptake and effectiveness.

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.

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 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)

Respiration induced by substrate and bacteria diversity after application of diuron, hexazinone, and sulfometuron-methyl alone and in mixture.

After application, herbicides often reach the soil and affect non-target soil microorganisms, decreasing their population, diversity or affecting metabolic activity. Therefore, laboratory studies were performed to evaluate the effects of diuron, hexazinone and sulfometuron-methyl alone and mixed upon carbon transformation by soil microorganisms in clayey and sandy soils and the effect on bacterial diversity and structure. Control treatment without herbicide application was also performed. Sub-samples from the control and herbicide treatments (10 g - in triplicate) were collected before herbicide application and 7, 14, 28 and 42 days after treatment (DAT), then 1 mL of 14C-glucose solution was applied. The released 14CO2 was trapped in 2 M NaOH solution and the radioactivity was analyzed by liquid scintillation counting (LSC), 12 h after glucose application. The effect of herbicides on bacterial diversity was evaluated by T-RFLP. The experiment was conducted in a complete randomized design. Hexazinone did not affect 14CO2 evolution. Diuron showed a greater 14CO2 evolution in sandy and clayey soil, while sulfometuron-methyl led to an increase in sandy soil, at 42 DAT. A greater evolution of carbon was observed in the treatment with herbicide mixture in sandy soil, compared with the same treatment in clayey soil or control. However, the herbicide mixture application did not affect the soil biological activity measured by the respiration rate induced by substrate. On the other hand, the herbicide mixtures affected the bacterial diversity in both soils, being the strongest effect to diuron and sulfometuron-methyl in clayey soil and hexazinone in sandy soil.

Glyphosate, isolated or in associations, at agronomic performance and seed quality of the RR®2 soybean / Glifosato, isolado ou em associações, no desempenho agronômico e qualidade de sementes de soja RR ® 2

The "second generation" of glyphosate-tolerant soybean (RR®2 soybean) was developed through a different technique of insertion of the glyphosate-insensitive EPSPs gene. Information on the selectivity of glyphosate, alone or in combination, in RR2 soybean is lacking. This study evaluated the effects of glyphosate, isolated or in associations, applied at post-emergence (V4), at agronomic performance and seed quality of soybean cultivar NS 6700 IPRO (RR2). The experimental design was randomized block with four replications and seven treatments, conducted in the field for two growing seasons. The treatments consisted of glyphosate herbicide, alone or in combination with clethodim, cloransulam, chlorimuron, lactofen and fluazifop, besides the control without application. Analysis was performed for crop injury, Soil and Plant Analyzer Development (SPAD) index, as well as variables related to agronomic performance (height, number of pods per plant, yield and 1,000-seed weight) and seed quality (vigor, germination, abnormal seedlings and dead seeds). An additional test was conducted with the same cultivar and treatments in a greenhouse in a completely randomized design with four replications. The herbicides did not affect agronomic performance and seed quality of RR2 soybean. Thus, the soybean cultivar NS 6700 IPRO (RR2) was tolerant to glyphosate, alone or combined with other herbicides applied in post-emergence (V4).(AU)

A "segunda geração" de soja tolerante ao glifosato (soja RR®2) foi desenvolvida por meio de uma diferente inserção do gene EPSPs insensível ao referido herbicida. Informações sobre a seletividade de glifosato, isolado ou em associação, são faltantes em soja RR2. Este estudo avaliou os efeitos do glifosato, isolado ou em associações, aplicado em pós-emergência (V4), no desempenho agronômico e na qualidade de sementes do cultivar de soja NS 6700 IPRO (RR2). Adotou-se o delineamento experimental de blocos ao acaso com quatro repetições e sete tratamentos, realizados no campo em duas safras. Os tratamentos consistiram no herbicida glifosato, isolado ou em associação com clethodim, cloransulam, chlorimuron, lactofen e fluazifop, além da testemunha sem aplicação. Foi realizada a avaliação dos sintomas de injúria e índice SPAD (Soil and Plant Analyzer Development), bem como de variáveis relacionadas ao desempenho agronômico (altura, número de vagens por planta, produtividade e massa de 1.000 sementes) e à qualidade das sementes (vigor, germinação, plântulas anormais e sementes mortas). Experimento complementar foi realizado com o mesmo cultivar e tratamentos em casa de vegetação em delineamento inteiramente casualizado com quatro repetições. Os herbicidas não afetaram o desempenho agronômico e a qualidade de sementes da soja RR2. Assim, o cultivar NS 6700 IPRO (RR2) foi tolerante ao glifosato, isolado ou em associação com outros herbicidas aplicados em pós-emergência (V4).(AU)

Leaching of Diuron, Hexazinone, and Sulfometuron-methyl Applied Alone and in Mixture in Soils with Contrasting Textures.

When herbicides are applied in mixture, interactions among them could potentially promote changes in herbicide behavior in the soil. Thus, application mode (isolated or in mixture) and soil texture (sandy or clayey) were investigated in the total leaching of the commercial mixture diuron + hexazinone + sulfometuron-methyl, and of each isolated compound. Experiments in soil columns also evaluated the movement of each herbicide and mixtures across soil layers. In the sandy soil, the greatest total leaching was observed with hexazinone compared to diuron and sulfometuron. Most of the applied diuron remained at the top layer of the soil, indicating that this herbicide has low soil mobility. Overall, our results show that hexazinone has greater leaching potential and mobility along the soil profile compared to diuron and sulfometuron. Our data can be used in assessing the fate of diuron, hexazinone, and sulfometuron alone or in mixture on natural ecosystems, under different soil types and application modes.

Uptake, translocation, and control of trumpet flower (Tecoma stans) with aminocyclopyrachlor.

To gain a better understanding of the physiology of the herbicide aminocyclopyrachlor in young plants of trumpet flower, the uptake and translocation were evaluated after the application of herbicide. This was determined by treating individual leaves with formulated herbicides plus (14)C-aminocyclopyrachlor after the application of the formulated herbicide. This experiment used a randomized experimental design with three replications. In addition, field studies were conducted to assess the effectiveness of foliar applications of aminocyclopyrachlor in association with metsulfuton-methyl. The plant absorbed 20% of the herbicide applied. The translocation percentage did not surpass 5% of the total amount applied. Only 1% of the herbicide applied was translocated to the roots. Rate of 40 + 13 g a.i. 100 L(-1) of aminocyclopyrachlor+metsulfuron-methyl was effective to control T. stans.

Interferências no consórcio de milho com Urochloa spp. / Interferences in the intercropping of corn with Urochloa spp.

Objetivou-se com este trabalho estudar a inter-relação entre a cultura de milho e cultivares de Urochloa spp. em consórcio, assim como a interferência de plantas daninhas nesses sistemas. O ensaio foi aleatorizado em três blocos em esquema de parcelas subdivididas, sendo as parcelas constituídas por sete sistemas de produção (Urochloa brizantha cv. 'Marandu' e cv. 'Piatã' e U. decumbens cv. 'Basilisk' em cultivo solteiro e em consórcio com o milho e cultivo solteiro de milho) e as subparcelas pelo controle de plantas daninhas (com e sem capina manual). Verificou-se que o estabelecimento dos consórcios de milho com as cultivares de Urochloa spp. não afeta os componentes de rendimento de produção, altura e produtividade do milho, assim como não reduz a comunidade de plantas daninhas, mas interfere na densidade populacional e massa de matéria seca por planta e por área das cultivares de Urochloa spp. Houve níveis de interferência semelhantes das plantas daninhas entre os sistemas de produção sem capina, devido à similaridade entre suas comunidades de plantas daninhas, com predomínio de espécies consideradas altamente competitivas, como Panicum maximum, e à predominância de espécies como Richardia brasiliensis e Ageratum conyzoides, associadas ao controle com capina.

This research was carried out to study the interaction between the corn and Urochloa spp. cultivars in association, as well as the interference of weeds in this cropping system. A randomized experiment in three blocks with split-plots design was conducted. The plots consisted of seven cropping systems (Urochloa brizantha cv. 'Marandu' and cv. 'Piatã' and U. decumbens cv. 'Basilisk' a sole culture and in association with corn as well as the sole culture of corn) and the split-plots by weed control (with and without weeding). It was found that the establishment of corn-Urochloa spp. cultivars association does not affect yield components such as height and grain yield, nor reduces the weed community, but interferes in the density, mass of dry matter per plant and per area of Urochloa spp. cultivars. There were similar levels of interference of weeds between cropping systems without weeding due to the similarity between the weed communities, showing the predominance of species considered as highly competitive such as Panicum maximum and also due to the low infestation with predominance of species such as Richardia brasiliensis and Ageratum conyzoides, associated with weed control.

Low glyphosate rates do not affect Citrus limonia (L.) Osbeck seedlings.

BACKGROUND: Glyphosate is used to control weeds in citrus orchards, and accidental spraying or wind drift onto the seedlings may cause growth arrest owing to metabolism disturbance. Two experiments were carried out to investigate the effect of non-lethal rates (0, 180, 360 and 720 g AI ha(-1)) of glyphosate on four-month-old 'Cravo' lime, Citrus limonia (L.) Osbeck, seedlings. Photosynthesis and the concentrations of shikimic acid, total free amino acids and phenolic acids were evaluated. RESULTS: Only transitory effects were observed in the contents of shikimate and total free amino acids. No visual effects were observed. CONCLUSION: The present study showed that glyphosate at non-lethal rates, which is very usual when accidental spraying or wind drift occurs in citrus orchard, did not cause severe metabolic damage in 'Cravo' lime seedlings.