Field experiments were conducted in 1993 to evaluate the effects of herbicide treatments and application timing on stale seedbed winter annual weed control. Studies were conducted at three locations, two in the Delta of Mississippi, and one in east Mississippi near Brooksville. The plot size was 13.3 by 40 ft in the Delta, and 12 by 25 ft in Brooksville. Treatments included Harmony Extra or Goal applied alone or in combination with either Gramoxone Extra or Roundup D-Pak. Each herbicide treatment was applied in the late winter and the early spring. Five weed species were evaluated for control: sibara [Sibara virginica (L.) Rollins], annual bluegrass (Poa annua L.), henbit (Lamium amplexicaule L.) at the Delta locations, and curly dock (Rumex crispus L.) and corn buttercup (Ranunculus arvensis L.) at Brooksville.

Sibara control was above 90% with all herbicides and timings. Annual bluegrass control was increased to above 80% when Gramoxone Extra or Roundup D-Pak were tankmixed with Harmony Extra or Goal, compared to less than 10% when the two latter herbicides were applied alone. All treatments controlled 80% of henbit, except the late winter applications of Gramoxone Extra and Roundup D-Pak applied alone. Corn buttercup control was greater than 90% for all treatments containing Gramoxone Extra, and the Harmony Extra plus Roundup D-Pak at both timings. All other treatments had less than 85% control. The early spring application of Goal plus Roundup D-Pak was the only treatment with 90% control of curly dock. The late winter application of Harmony Extra plus Roundup D-Pak had greater than 80% control. In conclusion, with the addition of Gramoxone Extra or Roundup D-Pak to Harmony Extra or Goal weed control was generally increased regardless of application timing.