Nine field experiments were conducted in 1998 and 1999 at the Tidewater AREC (TAREC), Suffolk, VA and at on-farm locations in southeastern Virginia to evaluate nutsedge management systems utilizing Roundup Ultra and MSMA with Roundup Ready^TM cottons. At all locations experiments were conducted in a randomized complete block design with 3 replications. Soil texture ranged from sand to sandy loam, organic matter from 1.1 to 3.7% and pH from 5.6 to 6.6.

Herbicide treatments as topical or directed sprays were applied with a delivery volume of 15 gpa. Treatments consisted of a topical application of either 32 fl oz/A Roundup Ultra (glyphosate) or 16 oz/A MSMA (6 lb ai/gal) to 2 to 4-leaf cotton. Topical treatments of Roundup Ultra were followed with no additional treatment, with 1 or 2 directed sprays of either Roundup Ultra (32 fl oz/A) or MSMA (2.66 pt/A) when cotton was at least 6 inches in height. Topical treatments of MSMA were followed with no additional treatment or with1 or 2 directed sprays of MSMA (2.66 pt/A) when cotton was at least 6 inches in height. In two trials (TAREC, 1998 and Chesapeake, Va, 1999) no soil applied herbicides were utilized on the experimental areas. In seven trials soil applied DNA herbicides (Prowl 3.3EC (pendimethalin) 1.5 pt/A or Treflan 4EC (trifluralin) 1.0 pt/A) and Cotoran 4L (fluometuron) (2.0 pt/A) were utilized on the experimental areas to reduce or eliminate annual grass and broadleaf weeds. Cotton lint yield was determined for the TAREC locations in 1998 and 1999. Yield was not determined at the on-farm locations.

Crop response and weed control were visually evaluated at mid-season (July 15 to August 15) at all locations utilizing a 0 to 100% scale. A visual rating of 0 represented no crop injury or weed control and a visual rating of 100 represented complete crop kill or complete weed control.