Monday, November 13, 2006

Postemergence Control of Feral Rye in Clearfield Wheat with ALS Inhibiting Herbicides.

Billie McKean and Case Medlin. Oklahoma State Univ, 2307 N Lakeview Court, Stillwater, OK 74075

Feral rye (Secale cereale L.) is a major weed problem in many Oklahoma wheat fields.  Feral rye infestations decrease the economic potential by lowering the amount of harvestable crop through direct competition and also dockage losses through contamination of the harvested grain. Due to its robust growth habit and similar growing season, it's a difficult weed in Oklahoma wheatfields to control.  The only labeled in-season chemical control practice for this weed is imazamox herbicide which requires the planting of imidazolinone-tolerant wheat.  Imazamox marginally controls feral rye.   Methods for improving control of feral rye are needed and should be researched.  The objective of this research was to evaluate feral rye control with various herbicide options in Clearfield winter wheat.  In 2006, a field study was conducted at OSU's North Central Research Station near Lahoma, Oklahoma.  The experimental design was a randomized complete block with four replications.  Treatments included imazamox (35 and 55 g ai/ha), imazapyr (70 and 195 g ai/ha), or nicosulfuron (55 or 70 g ai/ha) applied with two different surfactants (i.e. Dyn-A-Pak and Induce).  Treatments were applied postemergence in March 2006 with a CO2 backpack sprayer and a hand held boom.  Weed control and crop injury ratings were recorded from two weeks after application until harvest. There were no notable differences in weed control or crop response due to herbicide application rate or surfactant used. At 4 weeks after application (WAA), imazamox and imazapyr controlled feral rye at least 98%, regardless of rate or surfactant used.  Imazamox applications resulted in the lowest crop response ratings (less than 5%) of the products evaluated.  Crop injury from imazapyr ranged from 11% to 21%.  Nicosulfuron controlled feral rye less than 85% and resulted in at least 80% stunting of the crop.