Winter Weed Control Trial

Charles Stichler, Extension Agronomist

Warren Multer, IPM Agent, Glasscock Co.

Summary:

          Only four of 16 winter weed control treatments applied February 4, 2003 achieved satisfactory control of weeds after 50 days. Those treatments included: 1) 2,4-D ester, 2) 2,4-D ester + Touchdown IQ, 3) Touchdown IQ alone provided adequate weed control and 4) Gramoxone Max alone or mixed with Caparol provided some weed control. London Rocket, Pinnate Tansymustard, and Flixweed were the three predominate weeds in this treated test plot.

Objective:

          Find a weed control option or options for winter weeds in reduced tillage drip irrigated cotton in Glasscock Co. Tillage is greatly reduced under conservation or reduced tillage systems and cannot be depended upon for winter weed control.

Materials and Methods:

          On February 4, 2003 a trial was initiated to determine which chemicals would control winter weeds in cotton fields rotated from cotton into cotton the following spring. A portion of a drip irrigated field on was chosen and plots staked. The plots were two rows wide by 40 feet long. The small plot size was due to the area of weeds that was fairly uniform. Larger plots would have created great variability due to poor weed stands. The Agricultural Research Manager program was used to calculate rate, randomize plots and summarize the data. Treatments were established in a randomized complete block design, and each treatment was replicated three times. Materials were applied with a C02 backpack sprayer calibrated to apply 15.25 gal. of spray per acre at 30 psi. Nozzles were TurboTeeJet 11002 tips and were 19 inches apart on the boom. Speed of the applicator was timed by an audible metronome. The application was made at 10:00AM in the morning and wind speed was northerly at 7-10 mph and the temperature was about 45 degrees F. The wind was blowing directly down the rows, so side drift was negligible. The following three weeks were normal weather for west Texas. Temperatures were cool to cold with a light rain during the trial period. Ratings were visual percent control and made by Warren Multer and Charles Stichler.

Results and Discussion:            

          The results in the following table indicate percent control - dead plants - of henbit from 0-100% under the column “Control.” The column listed as “Herb Act” indicate on a scale of 1-10 the activity or injury to the weeds. Injury does not mean control since they can regrow and become established again.

          The lack of control with most of the products was surprising. The cold temperatures could be part of the problem, however we could not wait to spray until warmer weather of the weeds would be too large. After 50 days, 2,4-D Ester; 2,4-D Ester + Touchdown IQ and Touchdown alone at 40 fl. oz/A gave adequate control of most weeds in the plots. Caparol + Gramoxone; and Gramoxone alone came close to giving adequate control - but did not kill flixweed sufficiently. However, Gramoxone greatly stunted the flixweed - although it did not kill it - which was surprising.

          In other trials in Luling, Valor added to glyphosate (Touchdown IQ) and Karmex and Caparol gave good control of henbit and other weeds. Those tests were implemented the first of December and the weed spectrum different.

The following table lists the treatment list application rates and results.

   Ratings were made from 0 - 10.

         0 - no control or evidence of herbicide activity and

        10 - 100 % control of existing weeds.

Table 1.

Ratings were made by Warren Multer and Charles Stichler

Appreciation is given to Syngenta Crop Protection for grant funding to make this trial possible.

The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Texas Cooperative Extension is implied.