In Fall residuals for glyphosate-resistant Italian ryegrass, I wrote that I expected to see Italian ryegrass emerging soon based on the weather around the Mississippi Delta at that time.

Three weeks have passed with practically no rainfall, so there is still little to no Italian ryegrass emerged. I did find a few plants at one of our ryegrass emergence monitoring sites in Coahoma County, Miss., on Oct. 4. However, it is still too dry for this weed to be a problem yet this fall.

At Stoneville, Miss., the weed science group has worked extensively on developing management programs for glyphosate-resistant Italian ryegrass over the last few years. The best chance for reliable control is with residual herbicides applied in the fall.

The following contain management suggestions for 2010-11, based on research and others, are personal observations.

Apply residual herbicides when weather permits between mid-October and mid-November.

Based on research from 2009-10, fall residual herbicides can be applied too early when rainfall is high through the fall and winter months. This year, we began our fall residual herbicide programs on Sept. More than likely, the treatments applied in September will fail again this year, but this time it will be because the herbicide applications have received no rainfall for incorporation.

In previous years, applications in early-November provided excellent ryegrass control until spring. Historically, rainfall totals (and the chances of not being able to apply a herbicide) increase in November.

Because the probability of good days for field work decrease later in the fall, I suggest monitoring the 10-day weather forecast over the next couple of weeks and applying a residual herbicide one or two days prior to a day with a good potential chance of rain (if there is a day like that).

Dual Magnum, Treflan, and Command have performed most consistently for controlling glyphosate-resistant Italian ryegrass in fall residual herbicide research at Stoneville. Dual Magnum or Treflan should be utilized in fields that will be planted to cotton or soybeans the following year. Dual Magnum is the only fall residual herbicide for ryegrass that may be safely applied if the field will be planted in corn.

In fields where the 2011 crop will be rice, Command (2 pints per acre) is the only fall residual herbicide option. Do not apply Command or Treflan in the fall prior to planting corn and avoid use of Dual Magnum or Treflan in the fall prior to planting rice.

The Dual Magnum rate should be at least 1.33 pints per acre on lighter-textured soils, but it will need to be increased to 1.5 pints per acre on heavier soil. Treflan has performed well at 3 pints per acre on glyphosate-resistant Italian ryegrass, but 4 pints per acre was common in the past when Treflan was applied in the fall for rhizome johnsongrass control. Regardless of the rate, Treflan requires incorporation within 24 hours of application.