Glyphosate has been applied in European countries for over a decade between rows in olive groves and grape vineyards to control Conyza species [hairy fleabane (C. bonariensis), horseweed (C. canadensis) and Sumatran fleabane (C. sumatrensis)], however poor control has been observed in recent years. Glyphosate susceptible (GS) or resistant (GR) populations were assayed in each species. In addition, Conyza spp. control with alternative herbicides (alone or in mixture with glyphosate) over two years was also assessed. The GS populations of the three species were controlled with glyphosate field doses (1080 g ae ha −1). The GR hairy fleabane, horseweed and Sumatran fleabane populations were 15.0, 15.7 and 19.8 times more resistant, respectively, than their respective GS population. The shikimic accumulation of GS populations was 4-6 times higher compared with the GR Conyza populations, confirming the glyphosate resistance of the latter ones. The increase in the glyphosate dose did not control the GR Conyza populations, despite providing a higher dry growth reduction. Glufosinate and flazasulfuron, alone or mixed with glyphosate, were the effective options to control GR and GS populations of hairy fleabane and Sumatran fleabane. However, the GR horseweed population might have evolved multiple resistance to glyphosate and flazasulfuron in Hungary. The other herbicides (PSI, auxinic and PPO) showed an additive effect together with the control provided by glyphosate in the GS and GR populations; however generally, these herbicides could be applied alone at the rosette stage. Effective herbicides with modes of action different from glyphosate, except flazasulfuron for controlling horseweed, should be used to delay the selection of herbicide resistance in perennial crops in Europe. around the world (Heap, 2018). Glyphosate [N-(phosphonomethyl)-glycine] is the world's most successful post-emergence and non-selective herbicide (Duke, 2018). In Spain it has been widely used to control weeds in citrus orchards, olive groves, grape vineyards, and others perennial and annual crops (González-Torralva et al., 2010, 2014), as well as in path borders, railway lines, recreation areas and derelict sites (Urbano et al., 2007). This herbicide is absorbed through leaves and other young-green tissues, and translocated via phloem into meristematic tissues (Preston and Wakelin, 2008). Glyphosate is a potent inhibitor of 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) by blocking the biosynthesis of phenylalanine, tryptophan, tyrosine and others aromatic compounds in susceptible plants (Maeda and Dudareva, 2012).

The Pro106-Ser mutation governs the resistance to glyphosate of the R1 and R2 C barbata populations, but the impaired translocation could contribute to the resistance. These results confirm the first case of glyphosate resistance evolved in this species. © 2018 Society of Chemical Industry.

Resumo -São relatadas em diversos estudos variações na tolerância entre diferentes cultivares de mandioca a herbicidas. Objetivou-se nesse trabalho avaliar a tolerância de cinco cultivares de mandioca a aplicação em pós-emergência dos herbicidas fluazifop-p-butil e fomesafen isolados, e a mistura dos mesmos. Na primeira avaliação de intoxicação visual, aos 7 dias após a aplicação (DAA), foram constatados os sintomas mais visíveis de intoxicação das plantas de mandioca pela mistura dos herbicidas, bem como quando aplicou-se fomesafen isolado. Ao final do período de avaliação (35 DAP), as plantas apresentavam redução dos sintomas provocados pelos herbicidas em razão da recuperação da folhagem pelas cultivares. A mistura mostrou-se de elevada toxicidade a cultura provocando reduções no acúmulo de matéria seca foliar, caulinar, da parte aérea, diâmetro do caule, área foliar e altura das plantas das cultivares. Apesar dos elevados índices de intoxicação pelo herbicida fomesafen, não foram observadas variações significativas no acúmulo de matéria seca pelas cultivares. Tratamentos à base de fluazifop-p-butil não foram tóxicos à cultura promovendo resultados semelhantes aos observados para testemunha. Não se constatou diferenças no nível de tolerância aos herbicidas estudados, entre os cultivares mandioca. Palavras-Chave: Manihot esculenta, crescimento, seletividade, controle químico. Abstract -Several studies report herbicide tolerance variations of same species with different genotypes. Thus, this study aimed to evaluate the tolerance of five cassava cultivars to the post-1 Recebido para publicação em 09/08/2011 e aceito e 23/10/2011. 2 Parte da dissertação de mestrado do primeiro autor defendida pelo Programa de Pós Graduação em Produção Vegetal da Universidade Federal dos Vales do Jequitinhonha e Mucuri. Silva et al.220Rev. Bras. Herb., v.10, n.3, p.219-231, set./dez. 2011 emergence applications of fluazifop-p-butyl, fomesafen and the association of both products. In the first visual assessment of intoxication, the most visible symptoms in cassava plants of poisoning was observed at 7 days after application (DAA), caused by mixture treatment (fomesafen + fluzifop-p-butyl) and fomesafen isolated as well. At the end of the evaluation period (35 DAP), was observed reduction of intoxication signs and foliage recovery of all cassava cultivars tested. The mixture showed to be very toxic causing reductions in leaf dry matter, stem dry matter, shoots dry matter, stem diameter, leaf area and plant height. Despite a high rate of poisoning by the herbicide fomesafen, variations in dry matter accumulation was not observed Treatments based on fluazifop-p-butyl were not toxic to culture similar to plants of the check plots. There were no differences of tolerance level to herbicide treatments in the all cassava cultivars tested.

Resumo -O manejo inadequado das plantas daninhas é um dos principais fatores responsáveis pela baixa produtividade média de raízes da mandioca no Brasil. Nessa cultura, o método mecânico de controle das plantas daninhas é o mais utilizado em decorrência da baixa disponibilidade de herbicidas registrados para a mandioca. Na busca de alternativas para este problema este trabalho que teve como objetivo avaliar a tolerância de cultivares de mandioca à aplicação em pós-emergência de mesotrione. Para isso foi conduzido um experimento em casa de vegetação, em delineamento de blocos casualizados com quatro repetições. Adotou-se arranjo fatorial em esquema 5x5, constituído pela combinação de cinco doses do herbicida mesotrione e cinco cultivares de mandioca. Avaliou-se semanalmente a fitotoxicidade, altura, diâmetro de caule e número de folhas das plantas, e aos 35 dias após a aplicação (DAA) coletaram-se as plantas para determinação da matéria seca e área foliar das plantas. Os maiores valores de intoxicação visual foram observados aos 14 e 28 DAA, provocados pelas maiores doses do mesotrione. Estes sintomas consistiram em leve branqueamento das folhas mais novas das plantas. Aos 35 DAA as plantas apresentaram recuperação dos sintomas, principalmente pelo surgimento de novas folhas. Em nenhuma das doses avaliadas o mesotrione afetou as variáveis: altura, diâmetro do caule, número de folhas, área foliar e acúmulo de matéria seca de folha, caule, raízes e total; evidenciando a tolerância dos cultivares de mandioca ao herbicida. Palavras-chave: Manihot esculenta, crescimento, seletividade, manejo químico Abstract -Unsuitable weed management is one of the main factors responsible for low mean yield of cassava (Manihot esculenta Crantz) in Brazil. In this crop, mechanical weed control is the most commonly used, due to the lack of registered herbicides for cassava crop. In the search for alternatives to this problem, this work aimed to evaluate the tolerance level of cassavas cultivars to mesotrione herbicide applied in post emergence. A experiment was conducted, in green house conditions, in randomized blocks with four replications. A factorial scheme 5x5 was adopted, consisting of the combination of five dosages of mesotrione herbicides and five cassava 1 Recebido para publicação em 23/12/2011 e aceito em 22/02/2012.

Glyphosate is a cheap herbicide that has been used to control a wide range of weeds (4–6 times/year) in citrus groves of the Gulf of Mexico; however, its excessive use has selected for glyphosate-resistant weeds. We evaluated the efficacy and economic viability of 13 herbicide treatments (glyphosate combined with PRE- and/or POST-emergence herbicides and other alternative treatments), applied in tank-mixture or sequence, to control glyphosate-resistant weeds in two Persian lime groves (referred to as SM-I and SM-II) of the municipality of Acateno, Puebla, during two years (2014 and 2015). The SM-I and SM-II fields had 243 and 346 weeds/m2, respectively, composed mainly of Bidens pilosa and Leptochloa virgata. Echinochloa colona was also frequent in SM-II. The glyphosate alone treatments (1080, 1440, or 1800 g ae ha−1) presented control levels of the total weed population ranging from 64% to 85% at 15, 30, and 45 d after treatment (DAT) in both fields. Mixtures of glyphosate with grass herbicides such as fluazifop-p-butyl, sethoxydim, and clethodim efficiently controlled E. colona and L. virgata, but favored the regrowth of B. pilosa. The sequential applications of glyphosate + (bromacil + diuron) and glufosinate + oxyfluorfen controlled more than 85% the total weed community for more than 75 days. However, these treatments were between 360% and 390% more expensive (1.79 and 1.89 $/day ha−1 of satisfactory weed control, respectively), compared to the representative treatment (glyphosate 1080 g ae ha−1 = USD $29.0 ha−1). In practical and economic terms, glufosinate alone was the best treatment controlling glyphosate resistant weeds maintaining control levels >80% for at least 60 DAT ($1.35/day ha−1). The rest of the treatments, applied in tank-mix or in sequence with glyphosate, had similar or lower control levels (~70%) than glyphosate at 1080 g ae ha−1. The adoption of glufosiante alone, glufosinate + oxyfluorfen or glyphosate + (bromacil + diuron) must consider the cost of satisfactory weed control per day, the period of weed control, as well as other factors associated with production costs to obtain an integrated weed management in the short and long term.

ABSTRACT. In Brazil, infestations of crop areas with glyphosate-resistant (GR) sourgrass (Digitaria insularis (L.) Fedde) biotypes has risen significantly, increasing crop production costs. Glyphosate efficacy on three biotypes (GO, BA and MT) of sourgrass with suspected resistance was evaluated. A susceptible biotype (MG) was used as the control. The results confirmed that the MG and GO biotypes were susceptible to glyphosate (control > 90%). The MG biotype exhibited growth reduction and mortality by 50% (GR 50 and LD 50 , respectively) with mean glyphosate doses of 243.7 and 431.6 g ae ha -1. The resistance index of the biotypes with suspected resistance ranged from 2.8 to 6.1 in relation to GR 50 and between 1.4 to 26.7 in relation to LD 50 . The glyphosate susceptibility ranking of the sourgrass biotypes was MG < GO < MT < BA. The MT and BA biotypes demonstrated high glyphosate resistance levels, and the GO biotype had a high potential to develop resistance. Farmers should avoid the application of glyphosate overdoses to minimize the selection pressure on weeds. Eficácia do glyphosate em biótipos de capim-amargoso com indício de resistência coletadas em cultivos RR RESUMO. No Brasil, as infestações de áreas agrícolas com biótipos de capim-amargoso resistentes ao glyphosate, resultam em aumento significativo nos custos de produção das culturas. Avaliou-se a eficácia do glyphosate em três biótipos de capim-amargoso com indício de resistência (GO, BA e MT) a este herbicida. Um biótipo suscetível (MG) foi utilizado como controle. Constatou-se que os biótipos MG e GO foram suscetíveis ao herbicida (controle > 90%). O biótipo MG apresentou redução do crescimento e mortalidade em 50% (GR 50 e C 50 , respectivamente) nas doses de glyphosate de 243,7 e 431,6 g ha -1. Os fatores de resistência dos biótipos com indício de resistência oscilaram entre 2,8 a 6,1 em relação ao GR 50 ; e entre 1,4 e ≥ 26,7 em relação ao C 50 . A ordem de susceptibilidade dos biótipos de capim-amargoso foi MG < GO < MT < BA. Estes últimos apresentaram elevado nível de resistência ao glyphosate, e o biótipo GO têm potencial para desenvolvê-la. Portanto, os agricultores devem evitar a aplicação de superdose de glyphosate a fim de reduzir a pressão de seleção das plantas daninhas.Palavras-chave: controle químico, Digitaria insularis, dose-resposta, fator de resistência.

). Aos 45 dias após aplicação do herbicida, foram avaliados o CO 2 consumido, o carbono interno, a taxa fotossintética, a condutância estomática de vapores de água, a taxa de transpiração, a temperatura da folha e a eficiência do uso da água. O cultivar Platina mostrou-se menos afetado pelo mesotrione. Apenas neste cultivar as doses aplicadas de 144 e 216 g ha -1 não alteraram a taxa fotossintética das plantas. A temperatura da folha dos cultivares de mandioca também não foi alterada pelo herbicida; entretanto, observou-se redução na eficiência de uso da água para o cultivar Coqueiro.Palavras-chave: eficiência do uso da água, Manihot esculenta, taxa fotossintética.ABSTRACT -Efficiency of the photosynthetic rate and water use was evaluated in cassava cultivars (Coimbra, Platina, IAC-12, Coqueiro, and Cacau-UFV), sprayed with five mesotrione rates (0, 72, 108, 144, and 216 g ha -1 ). CO 2 consumed, internal carbon, photosynthetic rate, water vapor stomatal conductance, transpiration rate, leaf temperature, and water use efficiency were assessed 45 days after application of the herbicide. Platina cultivar was found to be less affected by mesotrione. Only in this cultivar, the applied rates of 144 and 216 g ha -1 did not alter the photosynthetic rate of the plants. The leaf temperature of the cassava cultivars was not affected by the herbicide, either; however, reduced water use efficiency was observed in the Coqueiro cultivar.

Stacked traits conferring dual herbicide resistance to the lines Rados and Helter come from the resistant parents. These R lines are potential tools for weed management in wheat production, mainly via herbicide rotation. © 2018 Society of Chemical Industry.