Cotton (var. DES 422 or DES 119) was planted in 1985-87 on a silt loam soil in an area which contained a natural infestation of johnsongrass. Trifluralin (Treflan 4E^®) at 1.0 (1985) or 0.75 lb a.i./A (1986, 1987) was applied preplant (PPI) to half the plots and soil incorporated 3 to 4 inches deep by disking twice, operating a field cultivator, and bedding in March each year. The area was rebedded prior to planting each year. Final seedbed height of approximately 3 inches was obtained with a bed conditioner at planting. Fluometuron (Cotoran 4L^®) applied preemergence, directed postemergence herbicides, cultivation, and hand hoeing were used to rid the entire test area of all weeds except johnsongrass. Treatments were arranged factorially using a randomized complete block design with three replications and each plot was four, 40-inch-spaced rows 40 feet long. Identical spot treatments were made to the same plots each year with and without Treflan. Spot treatments used were SC 1084 (Trophy 4E^®) in 1985 and clethodim (Select 2E^®) in 1986 and 1987. An adjuvant was added to all treatments at 1.25% V/V. Individual spot treatments were made with a 2-gallon hand-held "Spray-Doc^®" at concentrations of 0.12 and 0.24% v/v, a hand-held "Spot Gun" applicator at concentrations of 0.06 0.12, and 0.24% v/v, and an electrically weed-activated tractor-mounted spot applicator applying 0.0625 and 0.125 lb a.i./A at 10 gal/A broadcast volume when activated. A control treatment of 0.125 lb a.i./A was applied with a conventional boom sprayer calibrated to deliver a volume of 10 gal/A. Treatments applied by hand were made once each season, usually in late June. Two crop rows were sprayed per pass to "cover" johnsongrass foliage. The "Spot Gun" device delivered a measured volume of 5, 10, or 20 ml/squeeze in a straight stream which was directed toward the main clump(s) of the johnsongrass plants which were at or above the height of cotton plants. The tractor-mounted spot treatments were applied three times in 1985 and 1986 and two times in 1987. The application time was determined by visually estimating the amount of johnsongrass foliage extending above cotton plants. The conventional boom treatments were applied three times in 1985, one time in 1986, and two times in 1987 at or near the time of application for the tractor-mounted spot-spray treatments. Control of johnsongrass was determined by visually estimating the percent control at mid- (July) or late-season (September) on the two center rows of each plot. Visual johnsongrass control evaluations revealed spot treatments following Treflan averaged 22%, 40%, and 16% better control than those without Treflan for 1985, 1986, and 1987, respectively. The use of Treflan did not improve johnsongrass control for the following treatments: (1) the conventional boom (all years), (2) the 2-gallon hand treatment at 0.12 and 0.24% v/v in 1987, (3) "Spot Gun" treatments at 0.24% v/v and 5 ml/squeeze in 1985 and 1987, at 0.12% v/v and 10 ml/squeeze in 1985, and at 0.06% v/v and 20 ml/squeeze in 1985, and (4) the tractor-mounted device at 0.0625 and 0.125 lb a.i./A (all years). The spray volume required to spot treat by hand for each respective year averaged 1.8, 3.3, and 2.3 times more without Treflan as compared with the same treatments following the use of Treflan. The spray volume ranged from a low of 6.9 gal/A in 1985 with the 2-gallon hand application at 0.24% V/v with Treflan to a high of 208.8 gal/A in 1986 with the 2-gallon hand application at 0.12% v/v without Treflan. Cotton stand and seed cotton yield were also determined. Cotton stand was not affected by any treatment in any year. In 1985, seed cotton yield from the 2-gal hand treatment at 0.12% v/v without Treflan was lower than the same treatment or the tractor-mounted spot treatment of 0.0625 lb/A with Treflan. The conventional boom treatment without Treflan was lower in yield than the 2-gallon hand treatment at 0.24% v/v with Treflan. Less yield was obtained from the 2-gallon hand treatments at 0.12% v/v without Treflan when compared to most other spot treatments with Treflan. Yield in 1987 was less without Treflan as compared to spot treatments with Treflan except those applied with the tractor-mounted spot treatment device. The conventional boom treatment without Treflan produced similar yields to that obtained with Treflan. Highest yields resulted from treatments giving best johnsongrass control.

SC 1084 was not acceptable for johnsongrass control in 1985. The use of Select in 1986 and 1987 for spot treating johnsongrass was very effective, especially with multiple applications. Use of Treflan was not required for effective spot treatments.