Preemergence Control of Italian Ryegrass (Lolium multiflorum) in Wheat (Triticum aestivum)1

In the field, 14 soft red winter wheat cultivars responded differently to 1.1 kg ai ha –1 diclofop, 1.7 kg ai ha –1 BAY SMY 1500, and 0.42 kg ai ha –1 metribuzin applied POST. Diclofop and metribuzin did not injure any cultivar more than 10% on a silty clay soil. However, BAY SMY 1500 injured ‘Pioneer 2551’ and ‘Coker 983’ 39 and 21%, respectively, in March. All other cultivars were injured less than 10% by BAY SMY 1500. Early injury did not translate into yield loss in the cultivar tolerance study. In an application timing study for Italian ryegrass control, late-season ratings indicated better control with two-leaf applications than with PRE applications for all treatments. Delaying application to the three-tiller stage reduced control with BAY SMY 1500 or metribuzin, but not with diclofop. On the sandier soil at this location, wheat injury with 0.28 or 0.43 kg ha –1 metribuzin or 2.2 kg ha –1 BAY SMY 1500 was sufficient to reduce wheat yield compared with other treatments, despite good Italian ryegrass control.