Canada thistle injury with spring-applied herbicides in infrequently mowed fine fescue in Pennsylvania

摘要

Canada thistle [Cirsium arvense (L.) Scop] is a dicotyledonous species that infests grass stands by wind-disseminated seed and lateral roots that give rise to new shoots (Kraushar et al., 2012). Spring applications of triclopyr + clopyralid have showngood control of Canada thistle in Pennsylvania and are often used by golf course superintendents in infrequently mowed fine fescue (Festuca ssp.) rough (McDonald & Loughner, 2009). Studies in the western U.S. revealed that the pyridine carboxylic acid herbicide aminopyralid controlled Canada thistle 88 to 93%, whereas clopyralid provided 86% control when applied during late May to early June (Enloe et al., 2007). Little published information is available comparing products containing aminopyralid + 2,4-D, 2,4-D + triclopyr, or metsulfuron to aminopyralid alone and clopyralid-containing products for control of Canada thistle in fine fescue rough in Pennsylvania. Such information may provide superintendents with options for using different active ingredients for improved herbicide efficacy and resistance management.