|GOFF, BEN - University Of Kentucky|
|WITT, WILLIAM - University Of Kentucky|
|WILLIAMSON, JESSICA - University Of Kentucky|
|FLYNN, E - Dow Agrosciences|
|BURCH, PATRICK - Dow Agrosciences|
Submitted to: Forage and Grazinglands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2014
Publication Date: 12/22/2014
Citation: Goff, B.M., Aiken, G.E., Witt, W.W., Williamson, J.A., Flynn, E.S., Burch, P.L. 2014. Timing and rate of Chaparral treatment affects tall fescue seedhead development and pasture plant densities. Forage and Grazinglands. DOI: 10.2134/FG-2013-0001-RS.
Interpretive Summary: Ergot alkaloids produced by the fungal endophyte (Neotyphodium coenophialum) of tall fescue (Lolium arundinaceum) induce a toxicosis in livestock that reduces thriftiness, performance, and reproductive efficiency. These toxic alkaloids are found at the highest concentrations within the seedheads, which is of particular concern for beef producers of the southeastern USA where endophyte-infected ‘Kentucky-31’ tall fescue has been widely utilized for grazing. Cattle have shown to selectively graze upon these structures during periods of the growing season when the levels of alkaloids are at their highest. Emergence of highly toxic seedheads have shown to be suppressed with application of ChaparralTM herbicide (Dow AgroSciences). A small-plot study conducted at 2 locations to determine the effect of three rates of Chaparral on the production and seedhead densities of tall fescue when applied at three different times during the growing season. The experiment demonstrated maximum suppression by applying in the late spring treatment at a rate of 2 oz. per acre when tall fescue was on the early reproductive stages. This should provide livestock producers with a tool for the management and control of a highly toxic source of ergot alkaloids.
Technical Abstract: The herbicide Chaparral™ has been shown to suppress seedhead development in tall fescue (Neotyphodium coenophialum) pastures and reduce the symptoms of tall fescue toxicosis in cattle. However, little is known about the logistics of herbicide treatment on tall fescue pastures. The objective of this study was to determine the effect of three rates of Chaparral on the production and seedhead densities of tall fescue when applied at three different times during the growing season. Chaparral reduced tall fescue seedhead densities for all treatment dates, but the highest levels of suppression were achieved with a late spring treatment when tall fescue was in early stages of reproduction. This treatment also was the least detrimental to tall fescue populations. Chaparral applied to vegetative tall fescue in the early spring was the least effective at reducing seedhead densities, but significantly reduced the number of tall fescue crowns. Other species of grass also began to encroach into the tall fescue stands following treatment of the herbicide during the fall and early spring. Delaying Chaparral until later in the spring may be more effective for producers as it may allow for greater control of seedheads with less loss in tall fescue plants and the potential for higher forage yields. There was some success in suppressing tall fescue reproductive growth with a fall treatment of Chaparral, but more research may be needed to evaluate its merit over a late spring treatment.