Italian Ryegrass Control in Conventional and Glyphosate Tolerant Winter Canola.
Joshua A. Bushong, Mark C. Boyles, and Dr. Thomas F. Peeper. Oklahoma State Univ, 368 Ag Hall, Stillwater, OK 74078
Wheat producers in Oklahoma are experiencing increasing problems with Italian ryegrass. Growing winter canola in rotation with winter wheat increases herbicide options for controlling Italian ryegrass. Research at two sites in Oklahoma during the 2005-06 growing season evaluated herbicides for Italian ryegrass control in conventional and glyphosate tolerant winter canola. The experimental design at each site was a randomized complete block with four replications. Herbicide treatments were applied using a CO2 pressurized backpack sprayer with 93.5 L/ha of water carrier. Postemerge herbicides were applied with recommended adjuvants. Trifluralin at 1120 gai/ha was incorporated immediately before planting. Other treatments were applied postemergence in the fall or sequentially in the fall and late winter. Control was evaluated visually in late April when the winter canola was in late anthesis and the Italian ryegrass was heading. Trifluralin controlled Italian ryegrass 89 and 97% at the two locations. Italian ryegrass control with quizalofop p-ethyl applied only in the fall at 62 gai/ha was 55 and 79% at the two locations. Quizalofop applied only in late winter controlled Italian ryegrass 38 and 68%. Reduced control was attributed to high densities of more mature Italian ryegrass and dry conditions. Sequential applications of quizalofop controlled Italian ryegrass 80 and 89% at the two locations. Trifluralin applied prior to planting followed by quizalofop applied postemergence in the fall controlled Italian ryegrass 97 and 99% at the two locations. Italian ryegrass control with glyphosate applied in the fall at 630 gai/ha controlled the weed 76 and 82% at the two locations. Sequential applications of glyphosate controlled Italian ryegrass 97 and 99% at the two locations. Clethodim at 88 gai/ha applied only in the fall controlled Italian ryegrass 75 and 79% at the two locations. These data suggest that some Italian ryegrass emerged after the fall treatments were applied.