Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Plants, Soils, and Insects

Major Professor

G. Neil Rhodes Jr.

Committee Members

Gary E. Bates, Thomas C. Mueller, John C. Waller


This research quantified the level of seedhead suppression, injury, total ergot alkaloid changes, and forage quality changes in endophyte-infected tall fescue resulting from spring applications of aminocyclopyrachlor (ACP) plus metsulfuron (MET). Results indicated that ACP plus MET reduced tall fescue seedhead density 53 to 55% but also reduced yield 39 to 51% at spring harvest. ACP plus MET also reduced total ergot alkaloid concentration 28 to 34% and improved crude protein (CP) and relative forage quality (RFQ).

This research also determined the impact of ACP plus MET application timing and rate on tall fescue injury and weed control. Spring and early fall applications generally resulted in the greatest tall fescue discoloration and stunting while late fall applications resulted in the least discoloration and stunting. Increasing rates of ACP plus MET generally resulted in greater tall fescue injury in the spring, summer, and early fall application timings. ACP plus MET applied in the summer controlled horsenettle.

The third portion of this research determined the influence of fall vs. spring application timings of ACP plus MET on tall fescue seedhead suppression, injury, forage yield, and forage quality. Results indicated that ACP plus MET applied in late fall and early spring reduced tall fescue seedheads, but the late fall application had less of an impact on spring harvest yield. Increasing rates of ACP plus MET resulted in greater seedhead reduction and yield reduction. ACP plus MET improved CP and RFQ to a greater extent when applied in the spring than in the fall. Increasing ACP plus MET rate also led to higher CP and RFQ.

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Weed Science Commons