Over the next few weeks, winter wheat and barley will be greening and growing along with the winter annual weeds. We have had the opportunity to conduct a trial or two the last few years in Lancaster County focused on ALS-resistant chickweed. Last year, Glory (metribuzin) received a 24 (c) label for resistant chickweed control in winter wheat and barley and we included it in the test. We included 2 to 4 oz of Glory along with Harmony Extra. 

You will note that the Harmony Extra and the Powerflex HL alone only provided 50% to 60% chickweed control because of the resistance, as these are both ALS-inhibitors. Adding Glory increased control to 83% to 95% depending on the rate and combination. Specifically, Glory should be applied to winter wheat or barley at 2 to 4 oz/acre after the crop is beyond the 3-tiller stage but before jointing. This is a relatively low rate of metribuzin that is specifically targeting chickweed, but it will also suppress other winter annual broadleaves. We are not labeling above the 4 oz rate because there is some concern for crop injury, especially at higher rates. 

In general, barley is more tolerant than wheat, but tolerance within each species greatly varies. Many of the varieties listed on the Glory label are no longer on the market. For best results, apply metribuzin when chickweed is small (4-6 inches in diameter). Glory can be tank-mixed with other herbicides, such as Harmony Extra, 2,4-D, and Banvel/Clarity, etc., to broaden the spectrum of control. 

The other herbicide that is good on resistant chickweed is Starane Ultra, which is also labeled on wheat and barley. This product provided 91% control in last year’s trial (see Table). Both Glory and Starane Ultra have a 4 mo. recrop restriction for soybean, although Glory/metribuzin is labeled for soybean and at 4 oz/acre or less, there is little risk for soybean injury.

The other weed we were able to evaluate in last year’s trial was roughstalk bluegrass. Roughstalk bluegrass is a cool-season perennial with short stolons, but it mostly spreads by seed. In a nutshell, Powerflex HL at 2 oz/acre plus Glory provided 83% roughstalk bluegrass control, Maverick at 0.67 oz plus Glory was 91%, and Osprey at 4.75 oz plus Glory provided 87%. The Glory really did not add anything for bluegrass control. Bluegrass plants were severely stunted, but some were still alive, so it was unclear how much was killed vs. suppressed. 

In any case, all three of these herbicides did a nice job reducing the competition and stopping seed production in wheat. None of these grass herbicides are labeled for barley.

Effect of some herbicide treatments on ALS-resistant common chickweed and roughstalk bluegrass control. Trial conducted in Lancaster County, PA in 2013. Herbicides applied on April 10 and plots evaluated on June 5. All treatments included 0.25% NIS and Powerflex and Osprey treatments also included 2.5% AMS liquid. Means followed by the same letter are not statistically different at the 5% level.