-The aim of this research paper was to compare the growth of D. ciliaris and D. nuda crabgrass species under non-competitive conditions. To this end, two experiments were conducted, one from March -July 2010 and the other from February -June 2011. The experimental design of both trials was completely randomized making a factorial (2 seasons x 2 species crabgrass x 12 evaluation periods) with four replications. Assessments began at 15 days after sowing (DAS), and repeated weekly until 92 DAS. The variables evaluated were total dry matter (roots+leaves+stems), leaf area, leaf number and tiller. The results were submitted to analysis of variance and the absolute growth rate, relative growth rate and leaf area ratio were calculated using the means, which were adjusted regression models. The crabgrass species were significantly different in leaf area, leaf number, tiller number and dry matter per plant. D. ciliaris for all variables was statistically higher than D. nuda. Regarding the speed at which the growth of the species occurred, the absolute growth rate and relative growth rate of D. ciliaris was also greater than D. nuda. In addition, D. ciliaris also had a lower leaf area ratio indicating greater efficiency in converting light energy into carbohydrates. It can be concluded that D. ciliaris has a higher growth rate in conditions where there is no limitation of nutrients and water availability in relation to D. nuda, mainly due to D. ciliaris have greater leaf area, number of leaves and dry matter accumulation per plant.

Resumo -A manutenção da cobertura morta sobre o solo pode reduzir o potencial de infestação de plantas daninhas, assim como pode afetar a transposição dos herbicidas, a dinâmica de molhamento e a lavagem da palha pela água das chuvas. O trabalho teve como objetivos avaliar a dinâmica dos herbicidas diuron, metribuzin e tebuthiuron em diferentes regimes hídricos com e sem palha, e apontar as principais relações entre a presença ou ausência de palha na remoção dos herbicidas pela água da chuva e influência na eficácia de controle de plantas daninhas. O delineamento experimental foi o inteiramente casualizado em esquema fatorial 6 x 3 x 2, com quatro repetições, onde foram testados seis níveis para o fator chuva simulada (testemunha, 0, 5, 10, 20 e 20 + 20 mm), três herbicidas (diuron a 2,0 kg ha -1 ; metribuzin a 1,92 kg ha -1 e tebuthiuron a 1,2 kg ha -1 ) e duas quantidades de palha (0 e 10 t ha -1 ). Um dia após a aplicação dos herbicidas a palha foi removida dos vasos e as espécies Ipomoea grandifolia e Cucumis sativus foram semeadas, avaliando-se o controle aos 15 e 30 dias após a aplicação e 10 e 21 dias após a aplicação, respectivamente. O herbicida diuron foi menos eficaz nos tratamentos com palha emPcomparação ao metribuzin e tebuthiuron. A palha afetou de maneira significativa o controle das espécies I. grandifolia e C. sativus pelos herbicidas na ausência de chuva simulada. Chuva de 20 mm foi suficiente para remover os herbicidas da palha para o solo e promover níveis adequados de controle das plantas daninhas. Palavras-chaves: Irrigação, controle, diuron, metribuzin, tebuthiuron Abstract -Maintenance of mulch on the soil surface can reduce the potential for weed infestations, and may affect transposition of the herbicides, the dynamics of wetting and washing the straw by rainwater. The study had as objectives evaluate the dynamics of the herbicides diuron, tebuthiuron and metribuzin in different water regimes with and without straw, and point out the main relationships between the presence or absence of straw removal of herbicides by rainwater and influence on the effectiveness of weed control. The experimental design was completely randomized in factorial 6x3x2, with four replications, being tested six levels of the rain factor (control, 0, 5, 10, 20 and 20 + 20 mm), three herbicides (diuron 2000 g ha -1 ), 1 Recebido para publicação em

RESUMO -As plantas daninhas denominadas vulgarmente como corda-de-viola, pertencentes aos gêneros Ipomoea e Merremia, estão entre as mais importantes do Brasil. A identificação das espécies em campo, bem como o conhecimento da suscetibilidade específica a herbicidas, notadamente a flumioxazin, cuja tolerância específica é variável, são informações essenciais para uma recomendação racional de manejo. Com o intuito de determinar a suscetibilidade diferencial das convolvuláceas Ipomoea purpurea, Ipomoea hederifolia, Ipomoea triloba, Merremia cissoides e Merremia aegyptia, foram construídas curvas de dose-resposta com o flumioxazin, para obtenção dos controles percentuais de 50, 80, 95 e 99. Para isso, foram conduzidos dois experimentos em casa de vegetação; para cada espécie de planta daninha, os tratamentos herbicidas foram: 0, 7,81, 15,63, 31,25, 62,5, 125, 250, e 500 g de flumioxazin ha -1 , aplicados em condições de pré-emergência. A partir dos resultados, conclui-se que a suscetibilidade ao flumioxazin, em ordem decrescente, é: Merremia aegyptia < Ipomoea hederifolia < Ipomoea triloba < Ipomoea purpurea < Merremia cissoides. As doses que proporcionam 80% de controle são, respectivamente pela ordem de espécies, de 238,6; 173,1; 84,7; 43,8; e 16,8 g de flumioxazin ha -1 . Merremia aegyptia não é satisfatoriamente controlada pelo flumioxazin.Palavras-chave: Ipomoea spp., Merremia spp., corda-de-viola, controle.ABSTRACT -The weeds commonly known as morning glory belong to the genus Ipomoea and Merremia, and are among the most important in Brazil. The identification of these species under field conditions and knowledge of their specific susceptibility to herbicides, notably to flumioxazyn, presenting variable specific tolerance, is essential for the elaboration of rational management recommendations. Aiming to determine the differential susceptibility of the convolvulacea Ipomoea purpurea, Ipomoea hederifolia, Ipomoea triloba, Merremia cissoides and Merremia aegyptia, dose-response curves were built with the herbicide flumioxazyn to obtain the control levels of 50, 80, 95, and 99%. Thus, two experiments were conducted under greenhouse conditions, and for each species, the herbicide treatments were: 0; 7. 81, 15.63, 31.25, 62.5, 125, 250, and 500 g of flumioxazyn ha -1 , applied in pre-emergence conditions. Based on the results obtained, it was concluded that susceptibility to the herbicide flumioxazyn, in crescent order, is as follows: Merremia aegyptia < Ipomoea hederifolia < Ipomoea triloba < Ipomoea purpurea < Merremia cissoides. The doses providing 80% of control are respectively, according to the species order, 238.6; 173.1; 84.7; 43.8 and 16.8 g of flumioxazyn ha -1 . Merremia aegyptia is not satisfactorily controlled by flumioxazyn.

The occurrence of weed species with different levels of resistance to glyphosate has increasingly spread in agricultural areas. In Brazil, sourgrass is among the main species presenting issues in this regard. Thus, fast and reliable methods to detect glyphosate resistance are of special interest for this specie, either for research or rational management purposes. This study was carried out to verify the feasibility of using the germination test to detect glyphosate resistance in sourgrass. The experiment was conducted with two sourgrass biotypes, with different levels of susceptibility to glyphosate. The seeds were previously imbibed in solutions composed of 0, 0.1875%, 0.25%, 0.75%, 1.5%, 3% and 6% of glyphosate during two periods, five and ten minutes, and submitted to germination tests. The results indicate the germination test as a feasible and time-saving approach to evaluate glyphosate-resistant sourgrass, with results available in seven days.

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