Controlling Forage Weed Species Detrimental to Livestock Production

Abstract

Among the vast diversity of plants in the mid-South to which grazing livestock are exposed, there is a need to address certain species that are potentially harmful to livestock health and production. Field and greenhouse experiments were conducted on endophyte-infected tall fescue [Schedonorus arundinaceus (Schreb.) Dumort = Lolium arundinaceum (Schreb.) Darbysh.], a cool-season perennial forage, and perilla mint, (Perilla frutescens (L.) Britton) an herbaceous annual, to determine management techniques and control measures for healthier pasture and livestock systems. When seedheads reached maturity, spring and autumn glyphosate applications at 1.68 kg ae ha-1, coupled with autumn tillage and summer and winter cover crops effectively reduced tall fescue coverage to < 27% by 10 months after initial treatment (MAT) following a single year of management. If seedhead maturity is inhibited prior to first glyphosate application, tall fescue was reduced to <1% coverage 10 MAT. Despite seedhead suppression, at least 78% increase in coverage occurred in 24 months from remnant populations suggesting two years of renovation is required. Forage soybeans proved to be a valuable cover crop that maintained nutritive quality and mean dry matter yields of 5487 kg ha-1 across two years. Tall fescue seedheads were suppressed below 14% coverage (> 68% visual control) by nicosulfuron + metsulfuron (20 + 5 and 40 +11 g ai ha-1), imazapic (26 and 53 g ai ha-1), and sulfosulfuron (53 g ai ha-1) at 90 DAT. Reduction in forage heights may be expected, but was not consistently reduced when compared to untreated plots across locations. To control perilla mint, postemergence applications of aminocyclopyrachlor blends, glyphosate, picloram + 2,4-D, aminopyralid + 2,4-D, and 2,4-D alone provided superior control when applied prior to the plant’s reproductive growth stage. Picloram + 2,4-D also provided in-field soil residual activity and the most effective preemergence control, followed by aminocyclopyrachlor + chlorsulfuron, pendimethalin, and aminopyralid + 2,4-D for at least 141 DAT. Seed from weedy populations in north Mississippi tend to germinate in a range of night/day soil temperatures from 10/15 C to 25/30 C. Therefore, effective preemergence treatments should be applied by mid- to late- February in this region.