Glyphosate resistant crops were rapidly adopted by farmers since their introduction in 1996 and currently, greater than 90% of cotton and soybean crops are glyphosate resistant. Glyphosate has been an effective mean for controlling Palmer amaranth, however overreliance on glyphosate based systems resulted in weeds that can no longer be controlled with glyphosate. Palmer amaranth resistance to glyphosate has been confirmed in ten US states including Virginia's bordering neighbor North Carolina. The objectives of this study were to i) determine the spread of Palmer amaranth and evaluate awareness among farmers and agribusinesses of herbicide resistant weeds in Virginia; ii) determine the efficacy of commonly used cotton and soybean herbicides programs for Palmer amaranth control; and iii) conduct greenhouse experiments to quantify the level of glyphosate resistance in a Greensville County, Virginia population. Using a communication network of Virginia county extension agents and crop advisers, Palmer amaranth was found in 15 Virginia counties. A survey was conducted to evaluate awareness of herbicide resistance and management of weeds in Virginia. Ninety percent of producers had fields planted to Roundup Ready® crops for each of the last 3 years. One hundred percent of the responders claimed awareness of the potential for weeds to develop resistance to glyphosate, but when asked about how serious they consider weed resistance to herbicides, the responders average rating was of 7.9 (on a scale of 1 to 10 where 1 is "not at all serious" and 10 is "very serious" ). Eighteen percent of the responder population claimed no awareness of glyphosate resistant weeds documented in Virginia. Herbicide efficacy experiments were established in soybean and cotton fields infested with Palmer amaranth. In soybean, experiments were established in a field where Palmer amaranth was not adequately controlled with glyphosate in the previous year. Glyphosate applied at 0.87 + 0.87 + 1.74 kg ae ha⁻¹ at 1, 3, and 5 weeks after planting (WAP) provided 82 to 85% control in 2009, but only 23 to 30% control in 2010, a hot and dry year. Glyphosate applied after preemergence (PRE) herbicides improved control to 90 percent. Programs that included s-metolachlor + metribuzin applied preemergence and followed by glyphosate + fomesafen applied postemergence provided the best control (93%) at 8 WAP. Glufosinate based herbicide programs provided greater than 85% control when applied alone, and control increased to 95% when preceded by PRE herbicides. Many conventional control systems integrating different modes of action provided more than 80% control at final evaluation of Palmer amaranth in 2009 and 2010. In soybean, the most consistent and effective program was flumioxazin applied PRE followed by chlorimuron + thifensulfuron, which provided 99 and 82% control at final evaluation in 2009 and 2010, respectively. Cotton fields were heavily infested with Palmer amaranth, but control with glyphosate had historically been good. Glyphosate applied early postemergence, late postemergence, and late post-directed provided more than 95 percent control at final evaluation of Palmer amaranth. Preemergence applications of fomesafen, fluometuron, or pendimethalin + fomesafen provided 77 to 99 percent early-season control and control was complete with an additional postemergence glyphosate application. Glufosinate applied at 0.45 kg ha⁻¹ at 1 and 3 WAP or applied at 0.45 kg ha⁻¹ following a preemergence herbicide provided greater than 95% control. Greenhouse experiments confirmed Palmer amaranth resistance in a population collected from Greensville County, Virginia. In the first experiment, the resistant biotype's I₅₀ value (rate necessary for 50% inhibition) for dry weight was 1.47 kg ae ha⁻¹, which is 4.6 times greater than the susceptible biotype and 1.7 times the recommended use rate of glyphosate. For fresh weight, the I₅₀ value of the resistant biotype was 1.60 kg ae ha⁻¹, 4.7 times that of the susceptible biotype of 0.34 kg ae ha⁻¹. In the second experiment, the I₅₀ value for the susceptible population could not be determined because all glyphosate rates resulted in complete control. However, the resistant population required 1.01 and 1.30 kg ae ha⁻¹ of glyphosate to reduce the fresh and dry weight by 50%. / Master of Science

Field and greenhouse studies were conducted to investigate the role of water stress and time of glyphosate spraying in the variation in glyphosate efficacy. Data on water potential, foliar sugar and starch content, weather, and growth response were gathered for loblolly pine and four of its major competitors on 16 operationally sprayed tracts in Virginia. Glyphosate successfully released loblolly pine on all tracts. Control of white oaks was significantly related to foliar sugar concentration. Water potential and weather variables were not related to glyphosate efficacy for any species. Seedlings of loblolly pine, red maple, and sweetgum were raised in a greenhouse and nursery environment. At the end of the second growing season, three water stress treatments were imposed on each species at each of four glyphosate application dates. ¹⁴C-glyphosate was applied to a subsample of seedlings. Timing of application. water stress, or both significantly affected susceptibility of all three species to glyphosate. Efficacy for all three species corresponded to that expected from field data. Differences in species susceptibility to glyphosate were explained by differences in ¹⁴C-glyphosate translocation, but there was no difference among species in absorption of glyphosate. Efficacy changes across application dates followed seasonal changes in foliar sugar concentration. / Master of Science

Dissertation submitted in partial compliance with the requirements for the Masters Degree in Technology, 2010. / Water storage dams play an important part in the collection and purification of water destined for human consumption. However, the nutrient rich silt in these dams promotes rapid growth of aquatic plants which tend to block out light and air. Glyphosate is universally used as the effective non-selective herbicide for the control of aquatic plants in rivers and dams. Invariably there is residual glyphosate present in water after spraying of dams and rivers with glyphosate herbicide. The amount of residual glyphosate is difficult to determine on account of high solubility of glyphosate in water. Thus a method of sample preparation and a sensitive HPLC method for the detection of trace amounts of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) in water is required. A crucial step in sample preparation is pre-column derivitization of glyphosate with 9-fluorenylmethyl chloroformate (FMOC-Cl). For sample pretreatment, water samples were derivatized with FMOC-Cl at pH 9, extracted with ethyl acetate and sample clean-up was carried out by passing a sample through the SPE cartridge. For SPE, recovery studies were done to choose a suitable cartridge for glyphosate and AMPA analysis. The following cartridges were compared, namely, C18, Oasis HLB and Oasis MAX SPE cartridges. Best recoveries (101% for glyphosate and 90% for AMPA) were obtained using 500 mg of C18 solid-phase extraction cartridge. The eluent from SPE cartridge was injected into HPLC column. Three types of separation columns (namely; C18 column, silica based amino column and polymeric amino column) were compared for the separation of glyphosate and AMPA. The best separation of glyphosate and AMPA in water samples was achieved using a polymeric amino column and a mobile phase at pH 10 which contained a mixture of acetonitrile and 0.05 M phosphate buffer (pH 10) 55:45, (v/v) respectively. The method was validated by spiking tap water , deionized water and river water at a level of 100 μg/l. Recoveries were in the range of 77% -111% for both analytes. The method was also used in determining the levels of glyphosate and AMPA in environmental samples. This method gave detection limits of 3.2 μg/l and 0.23 μg/l for glyphosate and AMPA respectively. The limits of quantification obtained for this method were 10.5 μg/l and 3.2 μg/l for glyphosate and AMPA respectively. / Eskom Tertiary Education Support Programme (TESP) Durban University of Technology.

Mundialmente, a soja é considerada uma das principais fontes de produção de óleos e proteínas vegetais para alimentação humana e animal. Constitui-se atualmente um dos produtos de maior importância na economia brasileira. É notório o crescimento das áreas ocupadas pelas lavouras de soja no Brasil, que na safra 2014/2015 atingiram 32,09 milhões de hectares, com previsão de expansão para 32,20 milhões de hectares para a safra 2015/2016. Outro aspecto a ser salientado é que as lavouras de soja RR (Roundup Ready) corresponderam a 93,5%, da área total cultivada com soja no Brasil na safra 2014/2015. Cultivares STS (Soja Tolerante à Sulfoniluréias) contém um gene que aumenta a degradação de alguns herbicidas na planta, como por exemplo, o chlorimuron-ethyl, para o qual são posicionados tolerando doses até quatro vezes as doses recomendadas para cultivares não tolerantes, sem apresentar danos significativos. A soja STS foi desenvolvida através da técnica de mutagênese de sementes utilizando o agente alquilante etilmetanosulfonato (EMS), não sendo uma cultura transgênica. Os objetivos do presente trabalho foram: avaliar a seletividade do herbicida chlorimuron-ethyl aplicado em pós-emergência de soja RR/STS; avaliar a seletividade de herbicidas inibidores da ALS aplicados em pós-emergência de soja RR/STS. Para tanto foram conduzidos dois experimentos principais. O primeiro conduzido durante quatro safras (2011/2012 a 2014/2015), os tratamentos foram constituídos por sete doses do herbicida chlorimuron-ethyl (0, 15, 30, 45, 60, 75 e 90 g i. a. ha-1). Foi realizada avaliação das variáveis relacionadas ao desempenho agronômico (altura, número de vagens por planta, produtividade, e massa de mil sementes). O segundo durante a safra 2014/2015 no campo e casa de vegetação, em que a soja RR/STS foi submetida à aplicação de herbicidas inibidores da ALS, associados ou não ao glyphosate. Foi realizada avaliação de fitointoxicação, índice SPAD, bem como variáveis relacionadas ao desempenho agronômico para o experimento no campo (número de vagens por planta e produtividade). Os cultivares de soja CD 250 e CD 2630 RR/STS apresentaram-se tolerantes para aplicação, em pós-emergência (V4), do herbicida chlorimuron-ethyl até a dose de 90 g i. a. ha-1. O cultivar de soja CD 2630 RR/STS apresentou-se tolerante à aplicação, em pós-emergência, dos herbicidas utilizados, isolada ou em associação com glyphosate. Exceção feita ao metsulfuron-methy (2,4 g i. a. ha-1), associado ou não com glyphosate (960 g e. a. ha-1). / Worldwide soybean is considered one of the major sources of production of vegetable oils and proteins for food and feed. It currently is one of the most important products in the Brazilian economy. It is notable growth areas occupied by soybean crops in Brazil, that in the 2014/2015 season reached 32.09 million hectares, with expansion forecast to 32.20 million hectares for the season 2015/2016. Another aspect to be noted is that the RR soybean (Roundup Ready) crops corresponded to 93.5% of the total area cultivated with soybeans in Brazil in the 2014/2015 season. Cultivars STS (Sulfonylurea Tolerant Soybeans) contains a gene that increases the degradation of some herbicides in the plant, for example, chlorimuron-ethyl, to which are positioned tolerated doses up to four times the recommended dosages for nontolerant cultivars, without presenting significant damage. STS soybean was developed by seed mutagenesis technique using the alkylating agent ethyl methane sulfonate (EMS), not being a transgenic crop. The aims of this study were to evaluate the selectivity of the herbicide chlorimuron-ethyl applied post-emergence of RR/STS soybean; evaluate the selectivity of ALS-inhibiting herbicides applied postemergence of RR/STS soybean. Therefore, two main experiments were conducted. The first conducted for four seasons (2011/2012 to 2014/2015), the treatments were seven doses of the herbicide chlorimuron-ethyl (0, 15, 30, 45, 60, 75 and 90 g a. i. ha-1). Performed an assessment of variables related to agronomic performance (height, number of pods per plant, yield and mass of one thousand seeds). The second during the 2014/2014 season in the field and the greenhouse, where RR/STS soybean was subjected to application of ALS inhibitor herbicides, with or without glyphosate. It was conducted evaluation phytointoxication, SPAD index, as well as variables related to agronomic performance (number of pods per plant and productivity). The soybean cultivars CD 250 and CD 2630 RR/STS were tolerant to application, post-emergence (V4) of herbicide chlorimuron-ethyl up to a dose of 90 g a. i. ha-1. Cultivar CD 2630 RR/STS presented tolerance to application in postemergence herbicides used alone or in combination with glyphosate. Except for the metsulfuron-methy (2.4 g a. i. ha-1), associated or not with glyphosate (960 g a. e. ha-1).

Mundialmente, a soja é considerada uma das principais fontes de produção de óleos e proteínas vegetais para alimentação humana e animal. Constitui-se atualmente um dos produtos de maior importância na economia brasileira. É notório o crescimento das áreas ocupadas pelas lavouras de soja no Brasil, que na safra 2014/2015 atingiram 32,09 milhões de hectares, com previsão de expansão para 32,20 milhões de hectares para a safra 2015/2016. Outro aspecto a ser salientado é que as lavouras de soja RR (Roundup Ready) corresponderam a 93,5%, da área total cultivada com soja no Brasil na safra 2014/2015. Cultivares STS (Soja Tolerante à Sulfoniluréias) contém um gene que aumenta a degradação de alguns herbicidas na planta, como por exemplo, o chlorimuron-ethyl, para o qual são posicionados tolerando doses até quatro vezes as doses recomendadas para cultivares não tolerantes, sem apresentar danos significativos. A soja STS foi desenvolvida através da técnica de mutagênese de sementes utilizando o agente alquilante etilmetanosulfonato (EMS), não sendo uma cultura transgênica. Os objetivos do presente trabalho foram: avaliar a seletividade do herbicida chlorimuron-ethyl aplicado em pós-emergência de soja RR/STS; avaliar a seletividade de herbicidas inibidores da ALS aplicados em pós-emergência de soja RR/STS. Para tanto foram conduzidos dois experimentos principais. O primeiro conduzido durante quatro safras (2011/2012 a 2014/2015), os tratamentos foram constituídos por sete doses do herbicida chlorimuron-ethyl (0, 15, 30, 45, 60, 75 e 90 g i. a. ha-1). Foi realizada avaliação das variáveis relacionadas ao desempenho agronômico (altura, número de vagens por planta, produtividade, e massa de mil sementes). O segundo durante a safra 2014/2015 no campo e casa de vegetação, em que a soja RR/STS foi submetida à aplicação de herbicidas inibidores da ALS, associados ou não ao glyphosate. Foi realizada avaliação de fitointoxicação, índice SPAD, bem como variáveis relacionadas ao desempenho agronômico para o experimento no campo (número de vagens por planta e produtividade). Os cultivares de soja CD 250 e CD 2630 RR/STS apresentaram-se tolerantes para aplicação, em pós-emergência (V4), do herbicida chlorimuron-ethyl até a dose de 90 g i. a. ha-1. O cultivar de soja CD 2630 RR/STS apresentou-se tolerante à aplicação, em pós-emergência, dos herbicidas utilizados, isolada ou em associação com glyphosate. Exceção feita ao metsulfuron-methy (2,4 g i. a. ha-1), associado ou não com glyphosate (960 g e. a. ha-1). / Worldwide soybean is considered one of the major sources of production of vegetable oils and proteins for food and feed. It currently is one of the most important products in the Brazilian economy. It is notable growth areas occupied by soybean crops in Brazil, that in the 2014/2015 season reached 32.09 million hectares, with expansion forecast to 32.20 million hectares for the season 2015/2016. Another aspect to be noted is that the RR soybean (Roundup Ready) crops corresponded to 93.5% of the total area cultivated with soybeans in Brazil in the 2014/2015 season. Cultivars STS (Sulfonylurea Tolerant Soybeans) contains a gene that increases the degradation of some herbicides in the plant, for example, chlorimuron-ethyl, to which are positioned tolerated doses up to four times the recommended dosages for nontolerant cultivars, without presenting significant damage. STS soybean was developed by seed mutagenesis technique using the alkylating agent ethyl methane sulfonate (EMS), not being a transgenic crop. The aims of this study were to evaluate the selectivity of the herbicide chlorimuron-ethyl applied post-emergence of RR/STS soybean; evaluate the selectivity of ALS-inhibiting herbicides applied postemergence of RR/STS soybean. Therefore, two main experiments were conducted. The first conducted for four seasons (2011/2012 to 2014/2015), the treatments were seven doses of the herbicide chlorimuron-ethyl (0, 15, 30, 45, 60, 75 and 90 g a. i. ha-1). Performed an assessment of variables related to agronomic performance (height, number of pods per plant, yield and mass of one thousand seeds). The second during the 2014/2014 season in the field and the greenhouse, where RR/STS soybean was subjected to application of ALS inhibitor herbicides, with or without glyphosate. It was conducted evaluation phytointoxication, SPAD index, as well as variables related to agronomic performance (number of pods per plant and productivity). The soybean cultivars CD 250 and CD 2630 RR/STS were tolerant to application, post-emergence (V4) of herbicide chlorimuron-ethyl up to a dose of 90 g a. i. ha-1. Cultivar CD 2630 RR/STS presented tolerance to application in postemergence herbicides used alone or in combination with glyphosate. Except for the metsulfuron-methy (2.4 g a. i. ha-1), associated or not with glyphosate (960 g a. e. ha-1).

Canada fleabane is the second glyphosate-resistant (GR) weed species to be confirmed in Ontario. In 2010, GR populations were identified at eight sites in Essex County. In 2011 and 2012, 147 additional sites across eight counties were confirmed to be resistant. Twelve and seven sites were identified with multiple resistance (glyphosate and cloransulam) in 2011 and 2012, respectively, across five counties. In soybeans, preplant tankmixes of glyphosate (900 g a.e.ha-1) plus saflufenacil (25 g a.i. ha-1), saflufenacil/dimethenamid-p (245 g a.i. ha-1), metribuzin (1120 g a.i. ha-1), or flumetsulam (70 g a.i. ha-1) provided greater than 87% up to 8 weeks after application (WAA). Glyphosate rates 21 to 48X the label rate (900 g a.e. ha-1) were required for 95% control. Postemergence tankmixes did not provide acceptable control. In dicamba-tolerant soybean, dicamba applied preplant at 600 g a.e. ha-1 provided the most consistent control of GR Canada fleabane. / Monsanto Canada Inc., Grain Farmers of Ontario, Agricultural Adaptation Council

Made available in DSpace on 2016-12-08T16:44:47Z (GMT). No. of bitstreams: 1 PGPV14MA144.pdf: 861442 bytes, checksum: c0bd112f70401acc3674e49bcc979cf3 (MD5) Previous issue date: 2014-07-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of the present work is to analyze the response of plants of ryegrass (Lolium multiflorum) and wavy-leaved fleabane (Conyza bonariensis) to increasing doses of glyphosate to detect herbicide susceptible and resistant biotypes and to evaluate the physiological quality of seeds of these biotypes to verify the relationship between the resistance and the physiological seed quality of these weeds. Ryegrass and wavy-leaved fleabane plants were exposed to increasing doses of glyphosate, ranging from 0 up to 1440 g ae ha-1, and the fresh weight were weighted 21 days after application, for dose-response tests. Seeds were subjected to tests of physiological quality (germination, cold test and accelerated aging). The experimental design was completely randomized, using ten replicates for ryegrass and six replicates for wavy-leaved fleabane in the dose-response tests, and four replicates for tests of physiological seed quality. All studied biotypes of ryegrass and wavy-leaved fleabane showed differential response due to increasing doses of glyphosate. Ryegrass resistant biotypes showed resistance factors (RF) of 3.0 (Passo Fundo) and 8.3 (Vacaria), while the susceptible ones showed FR of 1.5 (Ponte Serrada) and 1.0 (Lages). Wavy-leaved horseweed resistant biotypes showed FR 2.0 (Papanduva) and 15.5 (Campos Novos), and the susceptible biotype FR 1.0 (Lages). In the tests of physiological seed quality, ryegrass biotype of Lages showed the best performance for germination (64%) and accelerated aging (86%) tests compared to the other biotypes. For the cold test, the biotype of Vacaria showed the best result with 86% of germination, while the biotype of Passo Fundo showed the worst results in all tests. Biotypes of wavy-leaved fleabane did not differ in germination. For Lages and Papanduva wavy-leaved fleabane, itwas found the biotypes responded positively to cold stress (66 and 61%, respectively). The biotype of Campos Novos, with high resistance to the herbicide, did not withstand the stress exposure, presenting similar to germination (34%) compared to the cold test (28%) result. The seeds of the wavy-leaved fleabane biotypes responded negatively to accelerated aging, in that the biotype of Lages showed the best result (12%), while biotypes of Papanduva and Campos Novos showed 4.0 and 2.0%, respectively. Biotypes of ryegrass with differential response to glyphosate present distinct percentage of germination and vigor of seeds, although it is not directly dependent on herbicide resistance. Susceptible biotypes of wavy-leaved fleabane and the biotype with low degree of resistance to glyphosate are more vigorous than the resistant biotype. The physiological seed quality of ryegrass and wavy-leaved fleabane is not directly related to the resistance to glyphosate, and the influence of environment is probably more significant than the resistance / Objetivou-se com o presente trabalho analisar a resposta de plantas de azevém (Lolium multiflorum) e buva (Conyza bonariensis) a doses crescentes do glyphosate para detecção de biótipos suscetíveis e resistentes ao herbicida e avaliar a qualidade fisiológica de sementes desses biótipos para verificar a relação entre a resistência e a qualidade fisiológica de sementes dessas plantas daninhas. Plantas de azevém e buva foram expostas a doses crescentes de glyphosate, variando de 0 a 1.440 g e.a. ha-1, com avaliação da massa fresca após 21 dias da aplicação. As sementes foram submetidas a testes de qualidade fisiológica (germinação, teste de frio e envelhecimento acelerado). O delineamento experimental utilizado foi o inteiramente casualizado, com dez repetições para o azevém e seis repetições para a buva no teste de dose-resposta e com quatro repetições para os testes de qualidade fisiológica de sementes. Todos os biótipos estudados de azevém e buva apresentaram resposta diferencial ao aumento de dose do herbicida glyphosate. Os biótipos de azevém resistentes apresentaram fatores de resistência (FR) igual a 3,0 (Passo Fundo) e 8,3 (Vacaria) enquanto os susceptíveis 1,5 (Ponte Serrada) e 1,0 (Lages). Os biótipos de buva resistentes apresentaram FR de 2,0 (Papanduva) e 15,5 (Campos Novos) e o biótipo susceptível FR de 1,0 (Lages). Nos testes de qualidade fisiológica o biótipo de azevém de Lages apresentou melhor desempenho para os testes de germinação (64%) e envelhecimento acelerado (86%) em relação aos demais biótipos. Para o teste de frio, o biótipo de Vacaria apresentou o melhor resultado com 86%. Enquanto que o biótipo de Passo Fundo apresentou os piores resultados em todos os testes realizados. Os biótipos de buva não se diferenciaram no teste de germinação. Para os biótipos Lages e Papanduva foi verificado que o vigor desses biótipos responderam positivamente ao estresse pelo frio (66 e 61% respectivamente). O biótipo de Campos Novos, com elevada resistência ao herbicida, não suportou a exposição ao estresse, apresentando resultado semelhante ao teste de germinação (34%) em relação ao teste de frio (28%). As sementes dos biótipos de buva responderam negativamente ao teste de envelhecimento acelerado, em que o biótipo de Lages apresentou o melhor resultado com 12%, enquanto os biótipos de Papanduva e Campos Novos apresentaram 4,0 e 2,0% respectivamente. Os biótipos de azevém com resposta diferencial ao glyphosate apresentam porcentagem de germinação e vigor de sementes distintos, porém não diretamente dependentes da resistência ao herbicida. Os biótipos de buva suscetível e com baixo grau de resistência ao herbicida glyphosate são mais vigorosos que o biótipo resistente. A qualidade fisiológica de sementes de azevém e buva não está diretamente relacionada com a resistência ao herbicida glyphosate, sendo a influência do ambiente, provavelmente, mais significativa do que a resistência

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-02-06T14:01:10Z No. of bitstreams: 2 Dissertação - Laís de Brito Rodrigues - 2016.pdf: 1513682 bytes, checksum: f083fb3e5a8cc62aa1d67ed3d78fbfe1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-02-06T14:01:33Z (GMT) No. of bitstreams: 2 Dissertação - Laís de Brito Rodrigues - 2016.pdf: 1513682 bytes, checksum: f083fb3e5a8cc62aa1d67ed3d78fbfe1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-02-06T14:01:33Z (GMT). No. of bitstreams: 2 Dissertação - Laís de Brito Rodrigues - 2016.pdf: 1513682 bytes, checksum: f083fb3e5a8cc62aa1d67ed3d78fbfe1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Glyphosate-based herbicides are the most commonly used worldwide due to their effectiveness and they are relatively non-toxic to non-target species. Unlimited and uncontrolled use of such pesticides can lead to serious consequences in terms of human health and ecological balance. We evaluated the acute toxicity of active ingredient glyphosate (GLI) and two glyphosate-based formulations, Roundup Original (RUP) and Glyphosate AKB 480 (AKB) on different organisms: seeds of cucumber (Cucumis sativus), lettuce (Lactuca sativa) and tomato (Lycopersicon esculentum), microcrustacean Artemia salina and zebrafish (Danio rerio) early life stages. For germination endpoint, L. esculentum presented sensitivity (EC50 = 702.10 mg/L) for AKB and L. sativa for GLI exposure (EC50 = 612.30 mg/l) whereas the three substances induced significant toxic effect on root elongation of all tested species. GLI, RUP and AKB induced significant toxicity to A. salina and were classified as Category III according to Globally Harmonized Classification System (GHS) criteria. However, RUP (LC50-48h of 39.4 mg/L) was more toxic than GLI (LC50-48h of 65.24 mg/L) and AKB (LC50-48h of 104.20 mg/L). For embryo-larval toxicity test, RUP proved be more toxic than AKB for mortality endpoint (LC50-96h of 28.23 and 75.33 mg/L, respectively) and GLI (LC50 > 100 mg/L) while for hatching parameter, AKB (EC50-48h of 6.23 mg/L) was more toxic than RUP (EC50-48h of 8.29 mg/L) and GLI exposure did not affect the hatching process. We concluded that active ingredient (GLI), AKB and RUP glyphosate-based formulations are phytotoxic and induce toxic effects in non-target organisms like A. salina and zebrafish early life stage. In addition, our results shows the evaluation necessity of glyphosate-based formulations, once they present different toxic potentials on different organisms. / Herbicidas à base de glifosato são amplamente utilizados em todo o mundo devido à sua eficácia e pelo fato de serem relativamente não-tóxicos para espécies não-alvo. O uso indiscriminado desses praguicidas podem levar a consequências graves em termos de saúde humana e desequilíbrio de ecossistemas. O presente trabalho avaliou a toxicidade aguda do ingrediente ativo (GLI) e duas formulações à base de glifosato, Roundup Original (RUP) e Glifosato de AKB 480 (AKB), em diferentes organismos: sementes de pepino (Cucumis sativus), alface (Lactuca sativa) e tomate (Lycopersicon esculentum), microcrustáceo Artemia salina e fases iniciais de desenvolvimento de zebrafish (Danio rerio). Para o endpoint de germinação, L. esculentum mostrou-se sensível a exposição ao AKB com CE50 de 702,10 mg/L e L. sativa para a exposição ao GLI com CE50 de 612,30 mg/L. No entanto, as três substâncias induziram efeito tóxico significativo no alongamento da raiz de todas as espécies testadas. GLI, RUP e AKB induziram toxicidade significativa para A. salina e foram classificados na Categoria III de acordo com critérios do Sistema Globalmente Harmonizado de Classificação (GHS). No entanto, o RUP (CL50-48h de 39,4 mg/L) foi mais tóxico do que GLI (CL50-48h de 65,24 mg/L) e AKB (CL50-48h de 104,20 mg/L). Para o teste de toxicidade com as fases iniciais de zebrafish, RUP (CL50-96h de 28,23 mg/L) provou ser mais tóxico para o parâmetro de mortalidade do que AKB (CL50-96h de 75,33 mg/L) e GLI (CL50 > 100 mg/L), enquanto que para o endpoint de eclosão, AKB (CE50-48h de 6,23 mg/L) mostrou-se mais tóxico do que o RUP (CE50-48h de 8,29 mg/L) e a exposição GLI não afetou a eclosão das larvas. Concluiu-se que, tanto o ingrediente ativo glifosato, quanto as formulações AKB e RUP foram fitotóxicos para as três espécies de sementes e induziram efeitos tóxicos em organismos não-alvo como A. salina e zebrafish. Além disso, nossos dados apontam para a necessidade de avaliação das diversas formulações a base de glifosato, uma vez que as mesmas apresentam diferentes potenciais tóxicos para diferentes organismos.

La fusariose de l'épi est une maladie grave des cultures céréalières du Québec. Il a été établi que la quantité de résidus de culture laissée par le travail du sol et l'application de glyphosate pouvaient augmenter l'intensité de cette maladie. L'objectif de cette étude était de déterminer l'effet du glyphosate, appliqué sur un précédent cultural de soya, sur l'intensité de la fusariose du blé et de l'orge et la production d'inoculum de Fusarium graminearum selon trois travaux du sol : labour à l'automne, travail réduit du sol au printemps et semis direct. L'expérience a été répétée sur deux années (2007-2008), à deux stations expérimentales localisées au Québec. Généralement, l'application de glyphosate n'a pas influencé significativement l'intensité de la fusariose ou la production d'inoculum de F. graminearum, quel que soit le travail du sol exécuté. En revanche, l'effet du cultivar était fortement significatif. Ce dernier facteur, combiné aux conditions climatiques et à l'inoculum aérien de F. graminearum présent au-dessus des parcelles, serait davantage associé à l'intensité de la maladie que l'application de glyphosate.

Casos reportados de buva com resistência ao glyphosate têm aumentado, ano após ano, a importância dessa planta daninha no cenário agrícola brasileiro. Com o intuito de entender alguns aspectos de sua biologia que resultem em manejo mais adequado, os objetivos deste trabalho foram: (i) identificar os períodos do ano em que ocorrem os maiores fluxos de emergência da buva e analisar seu crescimento e desenvolvimento em dois ambientes agrícolas distintos; (ii) avaliar os efeitos da cobertura vegetal e umidade em sua germinação e emergência; (iii) construir curvas de dose-resposta de um biótipo de Conyza bonariensis resistente ao glyphosate para herbicidas alternativos e (iv) avaliar as opções de manejo químico desse biótipo após o corte e rebrota. Para esses objetivos, experimentos foram conduzidos em campo e casa-de-vegetação nos municípios de Santa Cruz das Palmeiras, SP (SCP) e Não-Me-Toque, RS (NMT), entre maio de 2010 a maio de 2012. Em condições de campo, observou-se em SCP que a emergência da buva ocorre de forma escalonada, sendo mais concentrada no final do verão e início da primavera e a precipitação e a presença de pouca cobertura vegetal no solo parecem exercer mais influência que a temperatura. Em NMT, o fluxo de emergência é mais concentrado no inverno, em que a precipitação não é fator limitante, sendo a germinação e emergência favorecidas por temperaturas mais baixas. Nos dois locais, plantas que germinam na época mais fria do ano (julho) apresentam desenvolvimento inicial mais lento, com acúmulo de biomassa mais intenso e concentrado em torno dos 90-104 dias após a semeadura (DAS); plantas que germinam na primavera (setembro) também apresentam desenvolvimento inicial lento, porém seu crescimento é mais distribuído ao longo do tempo, com os picos de acúmulo aos 80-90 DAS. Em condições de casa-de-vegetação, a disponibilidade hídrica do solo foi mais importante para a emergência de plântulas de buva que a quantidade de cobertura vegetal (palha). Em solo úmido, menores quantidades de palha favorecem a emergência da buva em relação ao solo descoberto. Quantidades maiores de palha promovem supressão de sua emergência. A resistência ao glyphosate foi confirmada para o biótipo de C. bonariensis, coletado em SCP (biótipo B2) e a eficiência dos herbicidas alternativos foi diferente em função dos estádios de desenvolvimento desse biótipo no momento da aplicação. Os herbicidas metsulfuron, diclosulam, 2,4-D, dicamba, atrazine, glufosinate e paraquat foram os mais consistentes no controle do biótipo resistente, sendo que, no estádio mais avançado, a associação com glyphosate agregou no controle para metsulfuron, diclosulam e 2,4-D. Após o corte, controle mais eficiente da rebrota (biótipo B2) foi obtido quando a aplicação ocorreu no mesmo dia do corte que 7 dias depois e os tratamentos mais eficientes nas duas situações foram glyphosate + diclosulam, glyphosate + 2,4-D e 2,4-D. A associação de glyphosate aos tratamentos incrementou o controle da rebrota independentemente da época de aplicação. / Reported cases of glyphosate resistant hairy fleabane have increased its im-portance in Brazilian agricultural. To understand the key principles to effective man-agement, the objectives of this research were to: (i) analyze hairy fleabane growth and development patterns in two different agricultural environments during peak emergence, (ii) evaluate the effects of stover and soil moisture on seedling emer-gence, (iii) obtain dose-response curves for alternative herbicides in a Conyza bonariensis glyphosate-resistant biotype and (iv) evaluate chemical control options for this biotype after cutting and regrowth. For these objectives, experiments in the field and greenhouse were conducted in Santa Cruz das Palmeiras, Sao Paulo State (SCP) and Nao-Me-Toque, Rio Grande do Sul State (NMT), during May, 2010 to May, 2012. At SCP, the germination and emergence of hairy fleabane occurred cycli-cally, peaking more in late summer and early spring and influenced by increased rainfall. In addition, the presence of little crop residue or stover in the ground seemed to exert more influence than temperature. At NMT, emergence was more concen-trated during the winter, when precipitation is not a limiting factor. Germination and emergence were favored by lower temperatures. For both sites, plants that germinat-ed in the coldest season of the year (July) showed slower initial development, with a more intensive biomass accumulation and peaked around 90-104 days after planting. Plants that germinated in the spring (September) also showed slower initial develop-ment, but their growth was more evenly distributed over time, and peaked about 80-90 days after planting. In greenhouse conditions, soil water content was more im-portant for influencing seedling emergence of hairy fleabane than the amount of stover and the highest emergence was observed in moist soil. In the presence of moisture, lower amounts of stover increased seedling emergence of hairy fleabane compared to bare soil. The presence of large quantities of stover on the soil surface resulted in emergence suppression. Glyphosate resistance in Conyza bonariensis, biotype B2, was confirmed by dose-response curves with susceptible biotype. The efficacy of alternative herbicides was different depending on the stage of the resistant biotype at application timing. The herbicides metsulfuron, diclosulam, 2,4-D, dicamba, atrazine, glufosinate and paraquat were the most effective in controlling the resistant biotype. In later stages the association with glyphosate resulted in a better control with metsulfuron, diclosulam and 2,4-D. More efficient control of hairy flea-bane regrowth (biotype B2) was observed when herbicides were applied on the same day that the plants were cut than when applied 7 days after cutting. The most effec-tive herbicide treatments in both situations were glyphosate + diclosulam, glyphosate + 2,4-D, and 2,4-D alone. The association of glyphosate in the herbicide treatments increased control of hairy fleabane regrowth regardless of application timing.