Herbicide Systems for Johnsongrass Control

H.R. Hurst


 
ABSTRACT

These are results of the final 3 years of an experiment begun in 1978. In 1988-1990, preplant soil incorporated main-plot treatments of trifluralin (Treflan 4E ) at 0.5 and 0.75 lb ai/A, pendimethalin (Prowl 4E ) at 0.75 lb/A, and prodiamine at 0.5 lb/A (1988, 1989 only) were made in water at 20 gal/A. Treflan and Prowl were applied March 17, 1988; April 12, 1989; and March 21, 1990, to previously subsoiled and disk-harrowed (1988 only) field areas and soil incorporated 311 deep with a tandem disk harrow once-over at a 30, angle to the row direction. The soil was hipped 1 or 2 days later. Rows were re-hipped in 1988 2 days before planting. Beds were reduced to planting height with a row conditioner 1 day before planting. Prodiamine was applied to the prepared seedbed and soil incorporated 1-211 deep with a tandem rolling cultivator. 'DES 119' cottonseed was planted April 26, 1988; April 27, 1989; and May 2, 1990. Cyanazine (Bladex 4L ) at 1.2 lb/A was broadcast applied preemergence to the entire experiment each year. Broadleaf weeds were controlled with directed postemergence sprays of prometryn (Caparol 4L) or methazole (Probe 75DF) and hand hoeing as needed. All plots were cultivated to a 12-inch band on the row June 1 and 20, 1988; May 11 and 26 and June 20, 1989; and May 17 and June 6 and 21, 1990.

Sub-plot treatments of fluazifop (Fusilade 2000 1E at 0.5% volume/volume (v/v), clethodim (Select 2E) at 0.25% v/v, quizalofop (Assure 0.BE ) at 0.31% v/v, and no herbicides were applied as spot treatments in water by hand to "cover" johnsongrass foliage in each of the main-plot treatments each year. Non-ionic surfactant (Activate or X-77 ) was added to each treatment in 1988 (0.25% v/v) and 1989 (0.125% v/v) and to Fusilade and Assure in 1990 (0.125% V/V). An oil-surfactant (83-17) adjuvant (Agri-Dex ) was added to Select in 1990 (0.125% v/v). Spot treatments were applied June 6, 1988; June 7 and July 14, 1989; and June 18 and July 19, 1990.

When averaged across sub-plot treatments, the percent visual johnsongrass control in July with main-plot treatments resulted in greater control with Treflan 0.75 lb/A than all others in 1988 and Treflan 0.75 lb/A ,greater than Treflan 0.5 lb/A and prodiamine in 1989. There were no differences in 1990. When averaged across main-plot treatments, visual johnsongrass control was superior with all spot treatment herbicides when compared with no spot treatment. There were no differences among spot treatment herbicides in 1988. In 1989, Fusilade application resulted in greater control than Select or Assure. In 1990, Fusilade and Assure both gave superior control when compared with Select.

When averaged across preplant treatments, the spot treatment spray volumes (gal/A) used in 1988 were 29.4, 37.8, and 34.1 for Fusilade, Select, and Assure, respectively. In 1989, these values were 38.8, 33.2, and 24.3 for the June 7 application and 8.7, 18.9, and 14.9 gal/A for the July 14 application. Respective values for 1990 were 12.3, 17.0, and 2.0 gal/A for the June 18 application and 4.7, 16.8, and 9.6 for the July 19 application.

Cotton stand was not affected with any treatment. Seed cotton yield in treatments without spot treatment herbicide applications continued to be severely reduced from johnsongrass for the Prowl, Treflan 0.5 lb/A, and prodiamine treatments each year. In 1988, seed cotton yield with the main-plot treatment of Treflan 0.75 lb/A was higher than the other main-plot treatments when spot treatment applications were omitted. Yield was not different with this preplant treatment with any spot treatment application. In 1989 and 1990, the main-plot advantage from Treflan 0.75 lb/A without spot treatment did not occur. Seed cotton yields from main-plot treatments not followed with spot treatment were not different. Other combinations of main-plot and sub-plot treatments were generally similar in yield in all years except seed cotton yield from the combination of Prowl followed by (fb) Fusilade was less than that from Prowl fb Assure in 1988 and the yield from the combination of prodiamine fb Select was less than that from prodiamine fb Assure in 1989.



Reprinted from 1991 Proceedings Beltwide Cotton Conferences pg. 963
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998