Herbicide resistant plants may present changes in their physiology and aggressiveness. In order to evaluate the competitive differences of glyphosate resistant ryegrass, in a first experiment, resistant and susceptible biotypes grew in intra and interbiotypic competition in different environmental conditions (check, irradiance and water deficit). In a second experiment, these biotypes grew together in different proportions in the presence of wheat. The development of plants was evaluated in the first experiment by analyzing the number of leaves, height and dry biomass accumulated until flowering. In the second, the culture (tiller, nutrients and estimated productivity) and the ryegrass plants (quantitative and qualitative analysis) were analyzed through graphs and indices of grouping and competitiveness. Resistant ryegrass plants developed better in both conditions and experiments. In wheat, the presence of the potassium, sulfur and zinc nutrients and the final yield of plants in the coexistence with greater proportions of resistant plants were higher reduced. By the substitutive analysis, resistant ryegrass presented higher clustering coefficient and greater competitiveness than the susceptible biotype.Habilidade competitiva do azevém resistente ao glyphosate RESUMO: Plantas daninhas resistentes à herbicidas podem apresentar alterações na sua fisiologia e agressividade. A fim de avaliar as diferenças competitivas do azevém resistente à glyphosate, em um primeiro experimento, plantas resistentes e suscetíveis cresceram em convivência intra e interbiotípica, submetidas a diferentes condições ambientais (controle, restrição de irradiância e restrição hídrica). Em um segundo experimento, essas plantas cresceram juntas em diferentes proporções na presença do trigo. Avaliou-se, no primeiro experimento, o número de folhas, altura e biomassa seca acumulada por ocasião do florescimento de plantas. No segundo, analisaram-se a cultura (perfilhos, nutrientes e produtividade estimada) e as plantas de azevém (análise quantitativa e qualitativa), por meio de gráficos, índices de agrupamento e competitividade. Plantas de azevém resistente se desenvolveram melhor em ambas as condições e experimentos. No trigo, reduziu-se em maior grau o acúmulo dos nutrientes potássio, enxofre e zinco e a produtividade final de plantas na convivência com maiores proporções de plantas resistentes. Pela análise substitutiva, o azevém resistente apresentou maior coeficiente de agrupamento e maior competitividade do que o azevém suscetível. Palavras-chave: competição; resistência à herbicidas; Lolium multiflorum; Triticum aestivum; plantas daninhas Glyphosate resistant ryegrass competitive ability Rev. Bras. Cienc. Agrar., Recife, v.13, n.3, e5549, 2018 2/7

Cadillo is an invasive species in Florida pastures and natural areas. Despite its invasiveness, relatively few studies have evaluated cadillo management. Thus, the objective of this research was to determine effective POST herbicides for cadillo control in Florida. Greenhouse and field studies were conducted at the Range Cattle Research and Education Center near Ona, FL, in 2015 and 2016. In the greenhouse study, triclopyr-ester, aminopyralid, metsulfuron, 2,4-D amine, aminopyralid+metsulfuron, aminocyclopyrachlor+metsulfuron, and imazapyr+aminocyclopyrachlor+metsulfuron provided ≥80% control of cadillo 28 d after treatment (DAT). Aminocyclopyrachlor at 17 and 35 g ha–1 were the only treatments with <80% control, with 70% and 75% control, respectively. Similar results were reflected in cadillo dry biomass reduction. The herbicide treatments used in the field study were triclopyr-ester, aminopyralid, 2,4-D amine, aminocyclopyrachlor, and triclopyr+fluroxypyr. Most treatments provided excellent control in the field (≥90% control) 30 DAT, and by 60 DAT all treatments provided 100% control. Results from these studies suggest that cadillo is susceptible to many of the common POST herbicides utilized in pastures and natural areas in Florida.