Co-authored with Jeff Via, UT Extension Fayette County
Last week, on March 28, 2011, Extension agents in Fayette and Shelby County along with help from BASF put out a research plot targeting perennial foxtail. The plot is located on a field that was treated with varying rates of pedimethalin (Prowl H2O) and conducted where 1.5 quarts of Prowl H20 was applied along with glyphosate as a dormant spray.
Since a limited amount of research has been conducted in states south of Tennessee (where knotroot foxtail is more prevalent) and the results show that even the most effective treatments (Pastora or Pastora plus glyphosate) only provide suppression of the weed. We decided to do some research in state.
Pastora at 1.5 oz. along with different rates of glyphosate was applied to the field. We are also looking at other experimental herbicides. We will be monitoring and spraying the plot again with Pastora and glyphosate next week and will see how the different applications are affecting the perennial foxtail. At 1.5 qts. of Prowl H2O, the seedling foxtail are emerging everywhere. See picture below.
On the date that the research plot was conducted, the perennial foxtail was 8-10 inches in height. In a normal year, as already mentioned in the previous blog, our recommendation would be to apply a dormant spray for winter weeds and then apply Pastora at 1.5 oz./acre + glyphosate (8 oz./acre of a 4 lb./gal. product or equivalent) with a non-ionic surfactant at 1 qt./100 gal. 3-5 days after first cutting for knotroot foxtail “suppression”. This could then be followed by 1 oz./acre Pastora or Pastora plus (8 oz./acre of a 4 lb./gal glyphosate or equivalent) 10-14 days later if the weeds try to recover.
With the warmer than normal temperatures this year and the rapid early growth of the foxtail, troublesome fields need to be treated now.
Producers can expect reduced growth and discoloration of the bermudagrass following applications of Pastora or Pastora plus glyphosate. This is temporary and the bermudagrass will recover. Remember according to the Pastora label we cannot apply more than 2.5 oz./acre per season.
The agents in Fayette and Shelby County were called out and visited a field on April 3, 2012 where 4 quarts of Prowl H20 was used in combination in the dormant spray. The seedling foxtail was suppressed at this rate and at this point. However, the perennial foxtail is starting to put out seed heads.
Recommendations at this time are to use 1.5 oz. of Pastora with (8 oz. of 4lb./gal. glyphosate or equivalent) with a surfactant at 1 quart/ 100 gal. Depending on your perennial foxtail pressure, 10-14 days after that, apply 1 oz. Pastora with (8oz. of 4lb./gal. glyphosate or equivalent) and surfactant. We will be monitoring the research plot and make recommendations as the season progresses.
Pastora also has on the label that it can be applied in a 50-75 percent liquid N spray solution or with ammonium sulfate. The producer we visited with had some concerns with the Pastora and its recovery. With this being said, we recommended that he use the recommended rates above in the liquid N or with the ammonium sulfate after talking to a DuPont representative.
With that said, University of Tennessee research has shown that the liquid N does reduce injury but may be impractical if the grower is not set up for this. Regarding the ammonium sulfate, University of Tennessee research has shown that it did not reduce injury. As is the case with all agricultural chemicals, be sure to read and follow label directions and precautions.
