Investigation Into the Affect of Tank Mixtures On the Efficacy of Saflufenacil in Glyphosate Resistant Horseweed (Conyza Canadensis)

Glyphosate resistant (GR) horseweed (marestail) (Conyza canadensis) is continuing to pose problems for cotton growers in the state of Tennessee. , A new herbicide from BASF with the trade name Sharpen (a.i. saflufenacil) in earlier research appears to provide good pre plant burndown control of GR horseweed.  Therefore a study was initiated which evaluated saflufenacil at various rates tankmixed with glyphosate, glufosinate, and paraquat.
The study was conducted in 2009. Cotton variety Phytogen 375 WRF was planted on April 29. pre plant burndown applications were applied 7 days before planting on April 22. The Sharpen rates  evaluated were 0.25 oz/a, 0.5 oz/a. 1.0 oz/a (1x) , 2.0 oz/a.. Each of these Shrapen rates were tankmixed with Roundup PowerMax at 22 oz/A, Gramoxone Inteon at 40 oz/A and Ignite at 29 oz/A. These treatments were compared with Roundup PowerMax at 22 oz/A + Clairty at 8 oz/A the widely used horseweed burndown program by Tennessee cotton growers.  Cotton safety was evaluated by taking  cotton stand counts as well as percent injury. Horseweed control ratings were taken 7, 14, 21 and 28 days after application. 
GR horseweed was controlled with the 1 oz/A rate of Sharpen tankmixed with either Roundup PowerMax, Gramoxone Inteon or Ignite.  Sharpen at the 1 oz/a rate by itself did not provide acceptable control on horseweed. Visual cotton injury nor final cotton stand  was effected by the 1 oz/A Sharpen treatment alone or when in a tankmixture. All treatments tested provided the same cotton lint yield.  This is good news for Tennessee cotton growers in that they have a new option to control GR horseweed prior to planting cotton.