Impact of pasture herbicides on the seedling growth response of three tall fescue varieties

Chemical application is a viable and popular method for weed control, but the effectiveness of various herbicides depends on the target weed. The objectives of this study were to determine the appropriate herbicide for three tall fescue varieties that either do or do not contain endophytic fungi. Plants were split into six herbicide treatments and an untreated control for 7, 14, 21, and 28 days in a randomized complete block design experiment with four replicates. Herbicides evaluated were 2,4-D, aminopyralid, 2,4-D plus dicamba, metsulfuron plus chlorsulfuron, aminocyclopyrachlor, and metsulfuron plus aminopyralid. In all three tall fescue varieties, the application of 2,4-D, aminopyralid, 2,4-D plus dicamba, or aminocyclopyrachlor failed to reduce phytotoxicity, height, tiller number, and dry matter when compared with the untreated control. However, metsulfuron-containing treatments reduced all variables in every variety. We thus conclude that herbicides containing metsulfuron are the most phytotoxic to tall fescue.   Key words: Endophytic fungi, grass, weed control.