Earthworm injury test for in-situ biomonitoring of pesticides in biobeds.

Biobeds are presented as an alternative for good pesticide wastewater management on farms. This work proposes a new test for in-situ biomonitoring of pesticide detoxification in biobeds. It is based on the assessment of visually appreciable injuries to Eisenia fetida. The severity of the injury to each exposed individual is assessed from the morphological changes observed in comparison with the patterns established in seven categories and, an injury index is calculated. A linear relationship between the proposed injury index and the pesticide concentration was determined for each pesticide sprayed individually in the biomixture. The five pesticides used were atrazine, prometryn, clethodim, haloxyfop-P-methyl and dicamba. In addition, a multiple linear regression model (i.e., a multivariate response surface) was fitted, which showed a good generalization capacity. The sensitivity range of the injury test was tested from 0.01 to 630 mg kg-1 as the total pesticide concentration. This index is then used to monitor the detoxification of these pesticides in a biomixture (composed of wheat stubble, river waste, and soil, 50:25:25% by volume) over 210 days. The results are compared with standardized tests (Eisenia fetida avoidance test and Lactuca sativa seed germination test) carried out on the same biomixture. The results are also compared with data on the removal of pesticides. The injury test showed a better correlation with the removal of pesticides than the avoidance test and seed germination test. This simple and inexpensive test has proved to be useful for decontamination in-situ monitoring in biobeds.

Can herbicides of different mode of action cause injury symptoms in non-herbicide-tolerant young soybean due to simulated drift?

Accidental herbicide drift onto neighboring crops, such as soybeans, can seriously harm non-target plants, affecting their growth and productivity. This study examined the impact of simulated drift from ten different herbicides (2,4-D, dicamba, glyphosate, saflufenacil, oxyfluorfen, hexazinone, diuron, diquat, nicosulfuron, and isoxaflutole) on young soybean plants. These herbicides were applied at three simulated drift levels (1/4, 1/16, and 1/32) equivalent to recommended commercial doses, and the resulting symptoms were carefully evaluated. Simulated drift caused distinctive symptoms, including chlorosis, twisting, necrosis, and growth abnormalities, varying depending on each herbicide's mode of action. Dicamba proved more toxic than 2,4-D, and symptom severity increased with drift proportion, with all herbicides causing over 30% injury at the 1/16 proportion. Notably, 2,4-D, dicamba, glyphosate, hexazinone, and diquat exceeded the half-maximal inhibitory concentration (IC50) value, significantly reducing total biomass. Dicamba consistently caused 50% injury at all proportions, while hexazinone, at the highest dose proportion, led to plant mortality. Dicamba also had biomass accumulation beyond the growth reduction (GR50), whereas hexazinone exhibited less than 10% accumulation due to its capacity to induce plant mortality. This study emphasizes the importance of understanding herbicide drift effects on non-target crops for more effective and safe weed management strategies.

Can the Herbicide Dicamba Produce Oxidative Stress in the Native South American fish Jenynsia lineata at Environmentally Relevant Concentrations?

Dicamba (DIC) is one of the most applied auxin herbicides worldwide. Sublethal effects in the South American native fish Jenynsia lineata exposed to DIC concentrations close to environmental concentrations (0.03-30 µg/L) during 48 h were analysed thorough the evaluation of catalase (CAT), glutathione S-transferase (GST), superoxide dismutase (SOD) activities and malondialdehyde (MDA) and H2O2 levels for detecting potential oxidative stress. In gills MDA increased showing oxidative damage probably because of an inefficient antioxidant defense. This response evidenced the important role of gills as an organ of direct contact with waterborne contaminants. In addition, other changes in the biomarkers of oxidative stress were observed such as the inhibition of SOD activities in brain and the inhibition of GST in liver. These results show that short- term exposures to environmentally relevant concentrations of DIC could induce sublethal effects in native fish.

Soybean injury caused by the application of subdoses of 2,4-D or dicamba, in simulated drift.

2,4-D or dicamba can cause injuries and other deleterious effects on non-tolerant soybeans. Thus, the objective was to evaluate the potential for injury of subdoses of 2,4-D or dicamba, in drift simulation, for application in non-tolerant soybeans. Two experiments were carried out, one with 2,4-D and the other with dicamba. The treatments consisted of the application, in post-emergence of non-tolerant soybean, of subdoses 0; 1.35; 2.68; 5.37; 10.72; 21.45 and 42.9 g acid equivalent (ae) ha-1 2,4-D choline salt or dicamba diglycolamine (DGA) salt. Injury symptoms in plants, plant height and yield were evaluated, and the results were subjected to regression analysis. Polynomial fit was possible for the doses of both herbicides, with deleterious effects on soybean, with reductions in height and yield. The application of 2,4-D ≥ 10.72 g ae ha-1 was enough to cause injuries greater than 10% in plants, in simulated drift. The application of dicamba ≥1.35 g ae ha-1 was enough to cause injuries greater than 30% in plants, in simulated drift. For both herbicides, greater potential for injury and reductions in soybean yield were observed for the application of the highest doses (21.45 and 42.9 g ae ha-1).

Sensitivity of eucalyptus (Eucalyptus urograndis) plants to subdoses of the herbicide dicamba / Sensibilidade de plantas de eucalipto (Eucalyptus urograndis) à subdoses do herbicida dicamba

In view of the widespread increase in herbicide-resistant weeds, biotechnology companies have developed dicamba-tolerant soybean and cotton cultivars. This technology can, however, increase the risk of the productdrifting to adjacent areas.This study was developed with the objective of the to evaluate the phytotoxicity and biometric variables of young eucalyptus plants exposed to subdoses of the herbicide dicamba. The experiment was carried out under field conditions in Rio Verde, state of Goiás, Brazil. The treatments were represented by the application of 0 (control), 7.5, 15, 30, 60, 120 or 240 g ae ha-1of dicamba 45 days after the seedlings were planted in the field. In terms of phytotoxicity, the dicamba doses of 120 and 240 g ae ha-1caused greater damage to the eucalyptus plants in all periods of evaluation. The predominant symptoms were epinasty, increased number of shoots and necrosis and senescence of young branches and leaves. The herbicide doses of 120 and 240 g ae ha-1 significantly compromised plant height and diameter, number of branches and dry mass of leaves and roots, interfering with the growth and development of the eucalyptus crop. The results indicate that the effect of subdoses of the herbicide dicamba can interfere with the proper development of young eucalyptus plants, which may cause losses in the initial plantingphase and future losses for producers.(AU)

Em decorrência do aumento generalizado de plantas daninhas com resistência a herbicidas, empresas de biotecnologia desenvolveram cultivares de soja e algodão tolerantes ao herbicida dicamba. Essa tecnologia pode, no entanto, aumentar o risco do produto ser deslocado para áreas adjacentes às aplicadas. Neste trabalho objetivou-seavaliar a fitotoxicidade evariáveis biométricas de plantas jovens de eucalipto tratadas com subdoses do herbicida dicamba. O experimento foi realizado em condições de campo em Rio Verde, Goiás, Brasil. Os tratamentos foram representados pela aplicação de 0 (testemunha), 7,5, 15,30, 60, 120 ou 240 g ea ha-1de dicamba aos 45 dias após o plantio das mudas no campo. Em termos de fitotoxicidade, as doses de dicamba de 120 e 240 g ea ha-1causaram maiores danos às plantas de eucalipto em todos os períodos de avaliação. Os sintomas predominantes foram epinastia, aumento do número de brotações e necrose e senescência de ramos e folhas jovens. As doses de herbicidas de 120 e 240 g ea ha-1comprometeram significativamente a altura e diâmetro das plantas, número de ramos e massa seca de folhas, caules e raízes, interferindo no crescimento e desenvolvimento da cultura do eucalipto. Os resultados indicam que o efeito de subdoses do herbicida dicamba pode interferir no bom desenvolvimento de plantas jovens de eucalipto, podendo causar prejuízos na fase inicial de plantio e prejuízos futuros para os produtores.(AU)

Dynamics and weed control effectiveness of dicamba herbicide when applied directly on the soil and corn straw in Brazil.

Dicamba is a post-emergence herbicide commonly used to control broadleaves in cereal crops. However, a portion of the herbicide might reach soil surface, and many factors could affect its dynamics and effects. The objective of this research was to evaluate the dynamics of dicamba applied to the soil, to the soil and covered with straw and over the straw, in addition, to evaluate the weed control in pre-emergence. Two field experiments at different locations were conducted with dicamba. To quantify dicamba in the soil a LC-MS/MS system was used. In both experiments, rainfall and straw played a key role in dicamba soil dynamics and weed control. Dicamba in the soil was affected by presence of straw and accumulated rainfall after the application. Higher concentrations (254-432 ng g soil-1) in the soil 0-10 cm layers and greater leaching potential were found for the application in the soil compared to over the straw. The maximum concentration of dicamba (101.6-226 ng g soil-1) was found after 10 mm of rainfall for dicamba application over the straw. Around 60-70% of weeds were controlled with concentrations greater than 20 ng/g soil-1, in the presence or absence of straw.

Fitotoxicidade de subdoses do herbicida dicamba quando aplicado em pré-emergência da cultura da soja não-tolerante / Phytotoxicity of low doses of dicamba when sprayed in pre-emergence on non-tolerant soybean

As cultivares transgênicas de soja oferecem novas alternativas para a elaboração de programas de manejo de plantas daninhas, pois permitem a aplicação de herbicidas anteriormente considerados não seletivos à cultura, dentre estes, o herbicida dicamba. No entanto, é sabido que as cultivares não tolerantes são extremamente sensíveis a esse herbicida,de modo que a presença domesmo na área, por consequência de deriva de outras áreas ou limpeza incorreta de tanque, pode promover injúrias à cultura. Assim, este trabalho foi realizado com o objetivo de avaliar a suscetibilidade da soja não-tolerante ao dicamba quando submetida à deriva simulada deste herbicida em condição de pré-emergência da cultura. Três experimentos foram realizados, sendo dois em casa-de-vegetação e um em campo. O delineamento utilizado foi de blocos ao acaso, com quatro repetições. Em casa de vegetação, foramutilizadas as cultivares Agroeste AS 3590 IPRO e Nidera 7709 IPRO, simulando-se sete e seis doses de dicamba, respectivamente. A campo, foi utilizada a cultivar Monsoy 5917 IPRO, com seis doses. De forma geral, indiferente da variedade de soja, sintomas visuais foram observados nas plantas a partir da dose de 3,75 g ha-1de dicamba, sendo que a dose de 60 g ha-1foi considerada crítica. Abaixo desta dose, houve recuperação das plantas; no entanto, acima da mesma, houve redução na massa final das parcelas. Em campo, não foi registrada perda de produtividade da cultura da soja nas doses estudadas.(AU)

Soybean transgenic cultivars providea new alternative for elaborating weed management programs once they allow the application of herbicides previously considered non-selective to the crops, and between them, dicamba. However, it is well known that non-tolerant cultivars are extremely sensitive to this herbicidedueto spray drift or incorrect tank wash, which may promote severe injuries to the crop. Therefore, this work was developed toevaluatethe susceptibility of dicamba non-tolerant soybean submitted to simulated drift of this herbicide in pre-emergence conditions. Three experiments were conducted, two inside a greenhouse and one in field condition. Arandomized block design was adopted with four replicationseach. In the greenhouse, soybean cultivars Agroeste AS 3590 IPRO and Nidera 7709 IPRO were evaluated, simulating seven and six doses of dicamba, respectively. On the field, cultivar Monsoy 5917 IPRO was adopted, with six doses of dicamba. In general, besides soybean cultivar, visual symptoms were observed on plants up to 3.75 g ha-1of dicamba, and 60 g ha-1might be considered as the critical doses. Bellow this dose, plants were able to recover from symptoms; however, above this dose, a reduction on mass of dry matter was observed. In field conditions, no yield losses were observed for soybean, regarding thedoses evaluated.(AU)

Evaluation of an alternative sorbent for passive sampling of the herbicides 2,4-D and Dicamba in the air.

The present study aimed to evaluate the Strata-X® sorbent, commonly used in cartridges, through analysis by high-performance liquid chromatography coupled with mass spectrometry. Due to the different physical-chemical characteristics of the compounds, different conditions of chromatography and mass analysis were necessary. The developed methods were validated in terms of selectivity, linear range, linearity (coefficient of determination, r2), the limit of detection (LOD), the limit of quantification (LOQ), accuracy (recovery, %), and precision (RSD, %). The results allowed us to select efficient extraction methods, using methanol acidified to pH 2 with formic acid, to elute the herbicides 2,4-D and dicamba in both sorbent materials. Besides, the Strata-X® sorbent was efficient in the sorption of analytes; thus, we indicate it for potential use in air sampling as an alternative to XAD-2.

Searching an auxinic herbicide to use as positive control in toxicity assays.

Due to rising concerns for environmental and human health, many toxic compounds, such as auxin-based herbicides, have been tested in relation their toxicity effect. Especially cyto- and phytotoxic assays have been performed on a number monocot and eudicot plant species. In these approaches the toxicity level of the auxin is compared to a positive control - usually a commercial compound with known effects and chemical similarity to the target compound. However, many target compounds still lack an indication of an adequate positive control. Here, we evaluate the phytotoxic and cytotoxic effect of the auxins 2,4-dichlorophenoxyacetic acid, dicamba, and picloram in order test their potential use as positive controls. All tested auxinic herbicides showed clastogenic and aneugenic effect mechanisms. The results indicate 2,4-dichlorophenoxyacetic acid as the most phyto- and cytotoxic in the discontinuous method in Lactuca sativa L. and Allium cepa L., and also in the continuous method in A. cepa. Thus, we suggest 2,4-dichlorophenoxyacetic acid as a positive control for future mutagenesis studies involving new auxins. For studies with L. sativa in continuous method, we recommend the auxin picloram as positive control as this one was the only one which allowed the development of roots.

Effects of the emulsifiable herbicide Dicamba on amphibian tadpoles: an underestimated toxicity risk?

The effects of exposure to the herbicide Dicamba (DIC) on tadpoles of two amphibian species, Scinax nasicus and Elachistocleis bicolor, were assessed. Mortality and biochemical sublethal effects were evaluated using acetylcholinesterase (AChE), glutathione S-transferase (GST), glutathione reductase (GR), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities and thyroid hormone (T4) levels. The LC50 value at 48h was 0.859 mg L-1 for S. nasicus and 0.221 mg L-1 for E. bicolor tadpoles. After exposure to sublethal DIC concentrations for 48 h, GST activity increased in S. nasicus but significantly decreased in E. bicolor with respect to controls. GR activity decreased only in S. nasicus at all the tested DIC concentrations. AChE activity was significantly inhibited in both S. nasicus and E. bicolor tadpoles at 48 h. DIC also caused significant changes in transamination, as evidenced by an increase in AST and ALT activities in both amphibian species. T4 levels were higher in DIC-treated tadpoles of both species than in controls. The DIC-induced biochemical alterations in glutathione system enzymes and transaminases indicate lesions in liver tissues and cellular function. Moreover, the observed AChE inhibition could lead to the accumulation of acetylcholine, excessively stimulating postsynaptic receptors, and the increase in T4 levels in both species may indicate an overactive thyroid. The commercial DIC formulation showed a high biotoxicity in the two amphibian native species after short-term exposure, controversially differing from the toxicity level indicated in the official fact sheet data. This fact highlights the need for an urgent re-categorization and reevaluation of DIC toxicity in native species.

Physicochemical properties, droplet size and volatility of dicamba with herbicides and adjuvants on tank-mixture.

The adoption of dicamba-tolerant soybean varieties has increased the concern and demand for new drift and volatility reduction technologies. Potential spray nozzles and adjuvants should be studied to determine its effects on drift and volatility of dicamba tank-mixtures. The objective of this study was to evaluate physicochemical characteristics of spray solutions containing dicamba; to analyze droplet size effect with air induction nozzles; and to assess dicamba volatilization on soybean plants with a proposed methodology. Treatments included dicamba only and mixtures with herbicides and adjuvants. Dicamba mixed with lecithin + methyl soybean oil + ethoxylated alcohol adjuvant had the greatest efficacy potential among treatments considering tank-mixture pH, surface tension, contact angle and droplet size. The MUG11003 nozzle produced the coarsest droplet size and was better suited for drift management among nozzle types. The proposed volatilization methodology successfully indicated dicamba volatilization in exposed soybean plants and among the evaluated treatments, it showed greater volatilization for dicamba with glyphosate + lecithin + propionic acid adjuvant.

Simulated drift of dicamba and 2, 4-D on soybeans: effects of application dose and time / Deriva simulada de dicamba e 2, 4-D na soja: efeitos da dose de aplicação e tempo

The use of soybean varieties resistant to the herbicides dicamba and 2,4-D may lead to drifts towards areas grown with non-resistant varieties. The aim of this study was to evaluate the effects of dicamba and 2,4-D underdoses applied at the phenological stages V4 and R2 of soybeans. Two experiments were conducted with dicamba or 2,4-D in a randomized block design with four replications. The 4 × 2 + 1 factorial scheme was composed of four doses (0.028, 0.28, 2.8, and 28 g ae ha−1) of dicamba or 2,4-D applied at two phenological stages (V4 and R2) + a control treatment (without herbicide application). Dicamba underdoses caused damage to soybean crop affecting its vegetative growth and yield; the injuries caused by 2,4-D were neither enough to damage crop nor affect yield components. Dicamba underdoses applied at V4 caused injuries of up to 41%, while in R2 they reached 70%. Plant height decreased by up to 61% when treated with dicamba. Soybean yield was reduced by 29 and 76% when the simulated drift occurred at V4 and R2, respectively, and at a dose of 28 g ae ha−1 of dicamba. For the tested underdoses, only 2,4-D had no effect in soybean crop yield.

Com a inserção de variedades de soja resistentes aos herbicidas dicamba e 2,4-D os eventos de deriva destes herbicidas para áreas com variedades não resistentes será passível de ocorrência. Objetivou-se neste trabalho avaliar os efeitos de subdoses de dicamba e 2,4-D aplicados nos estádios fenológicos V4 e R2 da cultura da soja. Dois experimentos foram conduzidos com dicamba ou 2,4-D em delineamento experimental de blocos casualizados, com quatro repetições. Adotou-se o esquema fatorial de 4 x 2 + 1 composto por quatro doses (0,028, 0,28, 2,8 e 28 g ea ha-1) de dicamba ou de 2,4-D, aplicados em dois estádios fenológicos (V4 e R2) + um tratamento testemunha (sem aplicação de herbicida). As subdoses de dicamba provocaram danos na cultura da soja, afetando o desenvolvimento vegetativo e a produtividade, enquanto o 2,4-D não provocou injúrias suficientes para provocar danos que comprometessem a cultura, e desta forma, não afetou os componentes de produção. As subdoses de dicamba aplicadas no estádio V4 provocou injúrias de até 41%, enquanto em R2 chegaram a 70%. A altura das plantas reduziu em até 61% quando tratadas com dicamba. A produtividade da soja foi reduzida em 29 e 76%, quando a deriva simulada ocorreu nos estádios V4 e R2, respectivamente, e na dose de 28 g ea ha-1 de dicamba. Nas subdoses testadas somente o 2,4-D não afetou a produtividade da cultura da soja.

Toxicity to Rhinella arenarum tadpoles (Anura, Bufonidae) of herbicide mixtures commonly used to treat fallow containing resistant weeds: glyphosate-dicamba and glyphosate-flurochloridone.

Glyphosate (GLY)-dicamba (DIC) and GLY-flurochloridone (FLC) are herbicide mixtures which are widely used for treating fallow containing glyphosate resistant weeds. The aim of this study was to evaluate the acute toxic effects and the prevailing interactions on stage 36 tadpoles of the anuran species Rhinella arenarum when exposed to equitoxic and non-equitoxic combinations of these herbicide combinations. Experiments were realized using the following combinations of commercial formulations: 48% GLY-based Credit® + 57.71% DIC-based Banvel® and 48% GLY-based Credit® + 25% FLC-based Twin Pack Gold®. GLY-DIC and GLY-FLC equitoxic mixtures were assayed mixing each constituent with an equivalent individual toxicity able to induce the same lethality effect. After 96 h of exposure, GLY-DIC and GLY-FLC equitoxic mixtures presented toxic unit 50 values (TU50 96h) of 1.74 (confidence interval: 1.58-1.92) and 1.54 (confidence interval: 1.46-1.62) respectively, indicating the presence of a weak antagonistic interaction as TU values were greater than 1. For their part, most non-equitoxic combinations of GLY-DIC and GLY-FLC tested did not significantly differ from additivity, the only exception being when DIC and FLC were fixed at 0.33 TUs, where a weak antagonism was observed. Overall, results indicate that the toxicity of both GLY-DIC and GLY-FLC mixtures to R. arenarum tadpoles vary from additive to slightly antagonistic, depending on the proportion of constituting herbicide formulations present in the mixture.

Auxinic herbicides induce oxidative stress on Cnesterodon decemmaculatus (Pisces: Poeciliidae).

Pesticides might increase the production of reactive oxygen species (ROS). Dicamba (DIC) and 2,4-dichlorophenoxyacetic acid (2,4-D) are auxinic herbicides commonly applied in agroecosystems to control unwanted weeds. We analysed the oxidative damage exerted on the fish Cnesterodon decemmaculatus by an acute exposure to DIC- and 2,4-D-based herbicides formulations Banvel® and DMA®, respectively. The Endo III- and Fpg-modified alkaline comet assay was employed for detecting DNA damage caused by oxidative stress, whereas enzymatic and non-enzymatic biomarkers such as the activities of catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and glutathione content (GSH) were used to assess antioxidant response to these two herbicides. At the DNA level, results demonstrate that both auxinic herbicides induce oxidative damage at purines level. An increase on CAT and GST activities were detected in 48 h- and 96 h-treated specimens with both auxinics. GSH content decreased in fish exposed to DIC during 48 h and to 2,4-D after 96 h of exposure. Additionally, a diminished AChE activity in specimens treated with DIC and 2,4-D was observed only after 96 h. Total protein content decreased in fish exposed to both auxinics during 96 h. These results represent the first evaluation of oxidative damage related to DIC and 2,4-D exposure on a fish species as the Neotropical freshwater teleost C. decemmaculatus.

Genotoxicity by long-term exposure to the auxinic herbicides 2,4-dichlorophenoxyacetic acid and dicamba on Cnesterodon decemmaculatus (Pisces: Poeciliidae).

Long-term genotoxic effects of two auxinic herbicide formulations, namely, the 58.4% 2,4-dichlorophenoxyacetic acid (2,4-D)-based DMA® and the 57.7% dicamba (DIC)-based Banvel® were evaluated on Cnesterodon decemmaculatus. Primary DNA lesions were analyzed by the single-cell gel electrophoresis methodology. Two sublethal concentrations were tested for each herbicide corresponding to 2.5% and 5% of the LC5096h values. Accordingly, fish were exposed to 25.2 and 50.4 mg/L or 41 and 82 mg/L for 2,4-D and DIC, respectively. Fish were continuously exposed for 28 days with replacement of test solutions every 3 days. Genotoxicity was evaluated in ten individuals from each experimental point at the beginning of the exposure period (0 day) and at 7, 14, 21 and 28 days thereafter. Results demonstrated for first time that 2,4-D-based formulation DMA® induced primary DNA strand breaks after 7-28 days exposure on C. decemmaculatus regardless its concentration. On the other hand, DIC-based formulation Banvel® exerted its genotoxic effect after exposure during 7-14 days and 7 days of 2.5 and 5% LC5096h, respectively. The present study represents the first evidence of primary DNA lesions induced by two widely employed auxinic herbicides on C. decemmaculatus, namely 2,4-D and DIC, following long-term exposure.

Synergism of mixtures of dicamba and 2,4-dichlorophenoxyacetic acid herbicide formulations on the neotropical fish Cnesterodon decemmaculatus (Pisces, Poeciliidae).

Dicamba (DIC) and 2,4-dichlorophenoxyacetic acid (2,4-D) are two of the most applied auxinic herbicides worldwide, both individually and as part of a mixture. However, the toxicity and interactions achieved when applied as a mixture have not yet been characterised. The equitoxic and non-equitoxic acute toxicity exerted by binary mixtures of Banvel® (57.71% DIC) and DMA® (58.4% 2,4-D) on the Neotropical fish Cnesterodon decemmaculatus were evaluated. Results revealed mean values of 1.02 (range, 0.96-1.08) for the toxic unit (TU) that induced 50% mortality (TU50 96 h) to the fish exposed to binary equitoxic mixtures of the commercial formulations Banvel®-DMA®. These results suggest that the mixture is nearly concentration additive. Furthermore, results demonstrated the occurrence of synergistic interaction when non-equitoxic combinations of Banvel®-or DMA®-formulated herbicides were assayed. In this context and regardless of their concentrations, either Banvel®- or DMA®-induced toxicity were synergised by the presence of the counterpart within mixtures. The present study represents the first evidence of the lethality exerted by mixtures of two auxinic herbicides-namely, DIC and 2,4-D-reported to date for fish and other biotic matrices. When C. decemmaculatus is used as the target organism, a synergistic pattern is observed following exposure to a mixture of both herbicides.

Drift of 2, 4-D and dicamba applied to soybean at vegetative and reproductive growth stage / Deriva de 2, 4-D e dicamba aplicado em estágio vegetativo e reprodutivo da soja

The introduction of dicamba and 2,4-D-resistant soybean will increase the use of auxin herbicides for management of herbicide-resistant weeds, increasing risk of drift in non-target crops. The field experiment was conducted in 2016/17 to evaluate injury, growth, yield, germination and seeds vigor of soybean effects to simulated drift of 2,4-D and dicamba applied to soybean at the V3 and R2 growth stages. To simulate drift, 2,4-D was applied at 0; 5.16; 10.4; 20.8 e 41.5g ae ha-1 and dicamba at: 0; 3.7; 7.4; 14.9 e 29.8g ae ha-1. The injury of the dicamba is greater than 2,4-D, and the V5 stage is more susceptible to both herbicides. The greatest reductions in soybean yield follow the drift of dicamba in R2 and 2,4-D in V5. The physiological quality seeds of the soybean is reduced by dicamba and 2,4-D drift at both the V5 and R2 stages of the soybean. Soybean is highly sensitive to low rates of 2,4-D and dicamba at the vegetative or reproductive growth stages. Dicamba causes greater negative effects than 2,4-D on soybean. The low rate of 2,4-D and dicamba reduce germination and vigor seed on soybean offspring.(AU)

A introdução de cultivares resistentes ao dicamba e 2,4-D aumentará o uso destes herbicidas para o manejo de ervas daninhas resistentes a herbicidas, aumentando o risco de deriva em culturas não-alvo. Assim, o objetivo do trabalho foi avaliar a fitotoxicidade, crescimento, produtividade, germinação e vigor de sementes de soja exposta deriva simulada de 2,4-D e dicamba nos estágios vegetativo e reprodutivo da soja. O experimento foi conduzido a campo na safra 2016/17. Para simular a deriva, 2,4-D foi aplicado nas doses de 0; 5,16; 10,4; 20,8 e 41,5g e.a. ha-1 e dicamba nas doses de 0; 3,7; 7,4; 14,9 e 29,8g e.a. ha-1. A fitotoxicidade de dicamba é maior que 2,4-D, sendo o estágio V5 mais suscetível para ambos herbicidas. As maiores reduções na produtividade da soja sucedem a deriva de dicamba em R2 e 2,4-D em V5. A qualidade fisiológica das sementes de soja é reduzida em função da deriva de dicamba e 2,4-D em aplicação nos ambos estágios V5 e R2 da soja. A soja é altamente sensível a baixas concentrações de 2,4-D e dicamba nos estágios vegetativo e reprodutivo. O dicamba causa maiores efeitos negativos comparado com 2,4-D. Baixas concentrações de 2,4-D e dicamba reduzem germinação e vigor de sementes de soja.(AU)

Transcriptomic analysis of basidiocarp development in Ustilago maydis (DC) Cda.

Previously, we demonstrated that when Ustilago maydis (DC) Cda., a phytopathogenic basidiomycete and the causal agent of corn smut, is grown in the vicinity of maize embryogenic calli in a medium supplemented with the herbicide Dicamba, it developed gastroid-like basidiocarps. To elucidate the molecular mechanisms involved in the basidiocarp development by the fungus, we proceeded to analyze the transcriptome of the process, identifying a total of 2002 and 1064 differentially expressed genes at two developmental stages, young and mature basidiocarps, respectively. Function of these genes was analyzed with the use of different databases. MIPS analysis revealed that in the stage of young basidiocarp, among the ca. two thousand differentially expressed genes, there were some previously described for basidiocarp development in other fungal species. Additional elements that operated at this stage included, among others, genes encoding the transcription factors FOXO3, MIG3, PRO1, TEC1, copper and MFS transporters, and cytochromes P450. During mature basidiocarp development, important up-regulated genes included those encoding hydrophobins, laccases, and ferric reductase (FRE/NOX). The demonstration that a mapkk mutant was unable to form basidiocarps, indicated the importance of the MAPK signaling pathway in this developmental process.

Genotoxic effect of a binary mixture of dicamba- and glyphosate-based commercial herbicide formulations on Rhinella arenarum (Hensel, 1867) (Anura, Bufonidae) late-stage larvae.

The acute toxicity of two herbicide formulations, namely, the 57.71 % dicamba (DIC)-based Banvel(®) and the 48 % glyphosate (GLY)-based Credit(®), alone as well as the binary mixture of these herbicides was evaluated on late-stage Rhinella arenarum larvae (stage 36) exposed under laboratory conditions. Mortality was used as an endpoint for determining acute lethal effects, whereas the single-cell gel electrophoresis (SCGE) assay was employed as genotoxic endpoint to study sublethal effects. Lethality studies revealed LC5096 h values of 358.44 and 78.18 mg L(-1) DIC and GLY for Banvel(®) and Credit(®), respectively. SCGE assay revealed, after exposure for 96 h to either 5 and 10 % of the Banvel(®) LC5096 h concentration or 5 and 10 % of the Credit(®) LC5096 h concentration, an equal significant increase of the genetic damage index (GDI) regardless of the concentration of the herbicide assayed. The binary mixtures of 5 % Banvel(®) plus 5 % Credit(®) LC5096 h concentrations and 10 % Banvel(®) plus 10 % Credit(®) LC5096 h concentrations induced equivalent significant increases in the GDI in regard to GDI values from late-stage larvae exposed only to Banvel(®) or Credit(®). This study represents the first experimental evidence of acute lethal and sublethal effects exerted by DIC on the species, as well as the induction of primary DNA breaks by this herbicide in amphibians. Finally, a synergistic effect of the mixture of GLY and DIC on the induction of primary DNA breaks on circulating blood cells of R. arenarum late-stage larvae could be demonstrated.

Evaluation of the genotoxic activity of dicamba and atrazine herbicides in several Mexican and South American varieties of sweetcorn (Zea mays L.).

Corn is a major crop and various herbicides are used to maximize its production, which include a dicamba-atrazine mixture. This has great advantages, but can also induce DNA damage. Genotoxic activity was assessed by comet assay following application of two concentrations of dicamba-atrazine: 1000-2000 and 2000-4000 ppm. Apical meristem leaf nuclei from 119 varieties of sweetcorn plants from Mexico and South America, and from five commercial sweetcorn hybrids were used. Each accession comprised two individuals per concentration and two controls. Significant genotoxic activity (P < 0.001) was observed following treatment with 1000-2000 and 2000-4000 ppm compared to the negative control. There was no difference in the genotoxic activity induced by both 1000-2000 and 2000-4000 ppm concentrations in plants from Mexico and South America (P > 0.05) except (P < 0.05) in the 2000-4000 ppm treated plants from Mexico and the 1000-2000 ppm treated plants from South America. Sweetcorn hybrids showed significant genetic damage (P < 0.01) at all concentrations compared to the negative controls. Thus, the dicamba-atrazine mixture caused genetic damage to corn plants, and it suggested that Mexican sweetcorn is more sensitive to dicamba-atrazine than the maize varieties from South America. Neither hybrid status nor the origin avoids DNA damage caused by Marvel. Thus, maize can be useful as a biomonitor of genetic damage induced by chemicals and to identify possible phenotypes based upon the amount of genetic damage induced by herbicides and selection of resistant genotypes.