Texas Peanut Varietal Tolerance to Diclosulam and Flumioxazin


J.W. KEELING, B.L. PORTER, T.A. BAUGHMAN, W.J. GRICHAR, and R.G. LEMON.  Texas Tech University and Texas Agricultural Experiment Station, Lubbock; Texas Cooperative Extension Service, Vernon, Yoakum, and College Station.

Field studies were conducted near Denver City, Texas in 2001 to observe varietal tolerance to diclosulam (Strongarm) and flumioxazin (Valor) in Texas peanut.  In addition, diclosulam application timing was also evaluated.  Four high oleic peanut lines (Flavor Runner 458, Sunoleic 97R, TX 977006, Georgia Hi O/L) and a conventional variety (Tamrun 96) were used in this study.  Diclosulam is a new triazolopyrimidine sulfonanilide herbicide for use in peanut and soybean.  It has been reported to have broad-spectrum broadleaf weed control when applied preemergence (PRE), but some peanut injury has been observed.  Flumioxazin is an N-phenylphthalimide herbicide that acts as a protoporphyrinogen oxidase inhibitor.  In 1999 and 2000, early season diclosulam injury was observed on the Texas Southern High Plains at 0.024 and 0.048 lb ai/A PRE, but was not apparent at the end of the season.  Therefore, the objective of this study was to evaluate peanut varietal tolerance to diclosulam and flumioxazin and to also observe diclosulam timing.

Diclosulam at two rates, 0.016 and 0.024 lb ai/A, was applied both PRE and postemergence (POST), while flumioxazin was applied PRE at 0.063 and 0.094 lb ai/A.  Percent injury from PRE treatments were observed 14, 42, and 118 days after treatment (DAT) while POST treatments were evaluated 14, 58 and 90 DAT. Peanut grades and yields were determined at the end of the season.

At 14 DAT, diclosulam at 0.016 and 0.024 lb ai/A PRE injured peanut 10 to 40% in all varieties, except Tamrun 96.  At 42 DAT, diclosulam injury in the Flavor Runner 458 and the Sunoleic 97R varieties was    20 to 25%, while injury to the Georgia Hi O/L variety from diclosulam at 0.024 lb ai/A PRE was 35 to 45%.  At 118 DAT, injury decreased to < 5% in all varieties and yield was not affected by diclosulam PRE.  Less than 5% peanut injury was observed in all varieties from flumioxazin applied PRE at 14 DAT. No injury was observed at 42 and 118 DAT. Yield was not affected by any flumioxazin treatment.  At 14 DAT, diclosulam POST at both rates injured peanut  < 5% in all varieties and no injury was observed 90 DAT.  Yield was not affected by POST applications of diclosulam.

The same study was conducted near Yoakum and in Motley County, Texas. No peanut response was observed following any treatment of diclosulam and flumioxazin applied PRE at the Yoakum location.  When flumioxazin was applied PRE at the Motley County location, no injury was observed in any variety, at any rate, throughout the growing season and yield was not reduced.

These studies will be repeated in 2002 to evaluate diclosulam POST and to determine the factors that contribute to diclosulam and flumioxazin PRE injury.

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