Weed Management in Oklahoma Peanut


Oklahoma State University

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Peanut weed management trials were conducted at the Oklahoma Agricultural Experiment Station's Caddo Research Station near Fort Cobb in 2016. Peanuts were planted in early May and did not experience the heavy rainfall immediately after planting that occurred in 2015. While peanuts were planted in early May, cool, wet conditions did delay crop maturity and peanuts were not harvested until late October. Even with this delay in maturity, peanut yields were excellent in 2016. 
Trial (PFCS16-0l) evaluated various weed management programs with Zidua®. Peanut stand reduction and injury was 5 percent or less season long with all treatment combinations. The only treatments that controlled Texas panicum, PANTE, at least 85 percent prior to the POST applications were those that included Prowl H20® applied PRE followed by an At Crack® application 
of Gramoxone® followed by either Zidua® or Outlook®. The only treatment controlling PANTE 90 percent in August was Prowl H2O® PRE followed by an At Crack application of Gramoxone® 
+ Outlook® followed by a POST application of Cadre®. The only treatment controlling Palmer amaranth, AMAPA, over 85 percent was Prowl H2O® PRE followed by an At Crack application
of Gramoxone® + Zidua® followed by
a POST application of Cadre®. Only treatments including Prowl H2O® PRE followed by both an At Crack and POST herbicide combination adequately controlled ivyleaf morninglory, IPOHE,Trial PFCS15-02 evaluated the potential for the use of fluridone, SP1171, preemergence in peanut. This trial was maintained weed free. Unlike trials in 2015 stand reductions were less than 10 percent with all fluridone treatments in 2016. Peanut injury was much lower in 2016 with only fluridone applied at the 2X rate alone or in combination with Dual Magnum® or Valor® injuring peanuts 
10 percent or more mid-season. Late season injury was 5 percent or less with all treatments. While a yield reduction was observed with fluridone in 2015, no treatment effected yield in 2016. 
Trial PFCS15-03 evaluated the effects of 2,4-D + glyphosate on peanut. This trial was established to simulate drift and misapplication or tank-contamination. The trial was maintained weed free. Rates were applied from lX, 1 / 2X, 1 / 4X, 1 / 8X and 1 / 16X. All of these rates were applied at 30, 60 and 90 days after planting, DAP. Peanut stand reduction season long was less than 10 percent with all rates and application timings. Significant visual peanut injury was observed with the 1/2X and lX rates regradless of application timing. Visual peanut injury was greater than 10 percent season long with the 
1/ 4X rate applied at 30 and 60 DAP. Yield reductions occurred with 1/ 4X, 1/2X and lX applications at all timings. Yield reducations also occurred with 1/8X rate applied at 60 DAP. Care must be taken to minimize peanut to exposures of 2,4-D + glyphosate. 
Trial PFCS15-04 evaluated Anthem Flex® for weed control in peanut. Peanutstand redudion and injury was 6 percent or less season long with all treabnents applied. Initial PANTE control was 73 to 80 percent with Anthem Flex® applied PRE. Valor® + Prowl H20® was the only treatment that controlled Texas panicum 90 percent two weeks after planting. Select was applied POST2 after all treatments were applied to assist in controlling PANTE. After this application the only treatment that did not control Texas panicum at least 85 percent was Anthem Flex® applied POST alone at any of the three rates. The only treabnent that controlled AMAPA at least 90 percent late season was Anthem Flex PRE® at 3 fluid ounces per acre. Valor® + Prowl H2O Pre® followed by Gramoxone® + Outlook® AtCrack® followed by Cadre® was the only treabnent that controlled IPOHE over 95 percent late season. 
Appreciation is expressed to the Oklahoma Peanut Commission and the National Peanut Board for support of this project. Without the support of the OPC and the peanut producers of Oklahoma who contribute to the board through their checkoff dollars much of this research would not be possible. Thanks to Robert Weidenmaier and the farm crew at the Caddo Research Station for their assistance in conducting these trials. Support from BASF Crop Protection, FMC Corporation and SePro Corporation for their support of these projects is appreciated. 

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