Wheat Planting Weed Control Considerations
DR. LARRY STECKEL
JACKSON, TENN.
Between trying to harvest the large crop we have in the field and working around a long wet period in October very little wheat has been sowed. The great weather this past week will likely change all that and I would expect wheat planting to really get rolling.
As far as weed control in wheat there are some new additions this year. Zidua is now labeled as a delayed pre application for control of grass weeds in wheat as well as some small-seeded broadleaf winter annual weeds. The definition of delayed pre historically has varied but in Zidua’s case if the wheat has a ½” shoot it is good to go. In practical terms it would be 3 to 7 days after planting depending upon soil temperature. The rate of Zidua to use is 1 to 2 oz/A depending upon soil type.
The trick is to apply Zidua after that ½” shoot but before most of the ryegrass or poa has emerged. If you can hit that timing, Zidua will do a great job of controlling those weeds. If the application is later then Zidua will still provide some control of later emerging grass weeds. However a post application of Axial, Osprey, Finesse or Powerflex may be needed to control escapes. Please be mindful that ALS resistant ryegrass is starting to become more prevalent making Osprey, Finesse and Powerflex a little less reliable on that weed. If your field has a recent history where Osprey, Finesse or Powerflex was not effective on ryegrass then Axial is your best choice. On the other hand poa is often a lot more of a problem in wheat fields than ryegrass in our big cotton growing counties. In that case Osprey would be the best choice followed by Finesse and Powerflex. Axial is not a very effective poa herbicide.
The other very effective option for poa and henbit control in wheat is metribuzin. However, metribuzin really hammered a lot of our wheat last winter and a number of producers will likely be reluctant to use it this fall. Last winter was very cold and wet which reminded me of the winters we experienced in the 1970s. Metribuzin under that environment is much harder on wheat particularly for eroded hill sides that tend to heave more due to higher clay content. Who knows what the weather will be like this winter. However, caution would suggest to steer clear of metribuzin on fields that have a large percentage of eroded hill sides. If metribuzin is utilized on those type fields do not use rates over 2 oz/A. The big issue last year in those fields were on rates above 2 oz/A.
Another new option to help control henbit from a burndown application is Sharpen. Sharpen can be applied preplant to pre emergence in wheat. Sharpen tankmixed with glyphosate would be a more consistent burndown of henbit than Gramoxone. If applied pre emergence it can be tankmixed with Zidua.
Keep in mind that the weed spectrum at burndown needs to dictate the burndown utilized. If poa is the primary concern then Gramoxone is the best fit. If volunteer corn is the main issue then either Gramoxone or Finessee and if henbit is the main issue then glyphosate plus Sharpen. ∆
DR. LARRY STECKEL: Extension Weed Specialist, University of Tennessee