When I first came to Arkansas, weed control in wheat didn't require much beyond Hoelon in the fall, followed by 2,4-D in the spring. In fact, almost every acre in the state received at least one application of Hoelon. This, of course, has led to the current Hoelon-resistant ryegrass problem that we now have. This product is virtually gone from the market place due to resistance.
Over the past couple of years, we have replaced Hoelon with mostly ALS herbicides. These include: Finesse, Finesse G&B, Osprey and PowerFlex.
These are all excellent wheat herbicides with broader spectrums of weed control than just ryegrass alone. However, this family of herbicides is known for its rapid development of resistant weeds. We are seeing this problem increase across Arkansas.
In a recent survey of ryegrass populations from around the state it is obvious that the occurrence of ALS-resistant ryegrass populations is on the rise. Most of these populations are already resistant to Hoelon. That leaves a limited number of program approaches for ryegrass control in wheat, if you have both ALS and Hoelon resistance.
Before we get to the herbicides, it is important to remember some cultural practices that can help manage ryegrass problems. First of all, a single year of fallow or crop rotation and not allowing any ryegrass to go to seed is equivalent to about 90 percent control of ryegrass the following year. In addition, simply letting the first “flush” of ryegrass germinate and emerge prior to planting, then killing it either with tillage or preferably with chemicals, is also equal to about 80 to 90 percent ryegrass control.
There are a limited number of wheat herbicides with activity on ryegrass that have a different -- at least a slightly different -- mode of action than ALS or Hoelon. These include: Axial XL, Axiom and Prowl.
My preferred program for ALS- and Hoelon-resistant fields is to apply Axiom at one- to two-leaf wheat and then follow that with Axial XL + Prowl H20 at four-leaf to one-tiller ryegrass (this may be in the spring; if so, drop the Prowl H20). This has been more effective than the single shot option of just applying Axial XL + Prowl H20 in the fall on two to four-leaf ryegrass.
Ryegrass is the number one, two and three top weed problems in Arkansas wheat. The next big challenge is typically wild onion and garlic. We have several excellent to good options for this weed listed in the MP44.
You can find the MP44 on the web at www.uaex.edu or at your local county Extension offices. The 2012 version will be available in early January in print and sometime before that on-line.