The aim of this study was to compare the herbicidal efficiency of mixture florasulam + 2,4-D (Mustang 306 SE) in spring wheat cultivar Bryza, spring barley cultivar Antek and oat cultivar Cwał sown in monocrops and two-species mixtures. Field experiments were carried out in 2005-2007 at the Experimental Station in Winna Góra (52^o12’ N; 17^o27’ E), owned by the Institute of Plant Protection – National Research Institute in Poznań. Herbicyd Mustang 306 SE was applied in a dose of 0.5 dm³·ha^-1 at 3-5 leaf stage of cereals using the knapsack sprayer Gloria. The analysis of weed infestation of cereal stand was made with the quantitative-weighing method twice in the growing period (3-4 weeks after the application and 7-8 weeks after the application). Efficiency of herbicide action in mixtures was compared with its effectiveness in monocrops of individual species. From the analyses made it follows that of the cereal mixtures, the barley-oat mixture was infested in the least degree, and the wheat-oat mixture in the most degree. Strongest effect of cultivation in mixtures on reduction of weed infestation was noticeable on the control treatments, where the herbicide was not applied, whereas the cereal cultivation system (pure or mixed sowing) not always differentiated the herbicide efficiency. Cereal grain yields in mixtures after the application of mixture florasulam + 2,4-D were significantly higher than yields of at least one of the component, and yields of mixtures harvested from the control treatments exceeded grain yields of both cereal species in monocrops.

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