Our most troublesome weeds in wheat production are ryegrass and wild radish.  Ryegrass threatens production due to its resistance to several classes of herbicides.  There are 3 classes of herbicides that we can you for ryegrass control and resistance to 2 of these is widespread across Georgia.  Osprey and Powerflex have the same mode of action.  Axial and Hoelon are similar so resistance to one usually means resistance to both.  Finally we have two newer products Fierce and Zidua which both contain Pyroxasulfone so they should be treated the same as well.  Resistance to any of these classes occurs quickly if modes of action are not rotated.

The key to wheat weed control or any weed control is to start clean.  Tillage and Glyphosate are good options prior to planting.  Gramoxone can also be used after planting prior to emergence.  This is when it gets a little tricky.  After planting wheat at least 0.75″ deep and 80% of the wheat has germinated you can use 1.0 oz/A of Zidua.  This will only provide residual control and has to be activated prior to ryegrass germination.  Another option is to plant wheat between 1 and 1.5″ deep and use 1.5 oz/A of Fierce.  With Fierce you wait for wheat to be in the spike to 2-leaf stage.  This is the best option if ryegrass is already emerged but less than 1/4″.  Fierce has the active ingredient mentioned above and the same active as we find in Valor.  Therefore the chances of getting wheat injury are much greater.  If cool wet weather follows the application you will undoubtedly get injury and stand reduction.

Assuming you don’t have any resistance you can go in from the 3-leaf stage of growth to jointing with one of these options:  Axial XL 16.4 oz/A, PowerFlex HL 2.0 oz/A, or Osprey 4.75 oz/A.  Finally for emerged ryegrass control with residual you can use Axial XL 16.4 oz/A (assumes no resistance) + Zidua 1 to 1.5 oz/A.  For all of these recommendations ryegrass must be less than 1 tiller.  Be sure to follow the label instructions for rates, adjuvants and use of liquid nitrogen.

For Radish and other broadleaf weeds the options and flexibility are greater and resistance is not an issue at this time.  if Radish is less than 8” diameter and you need to also kill henbit, and chickweed you can spray wheat from 2- tiller through
full tiller with MCPA (12-16 oz/A) + Harmony Extra (MCPA rate based on 3.8 lb/A).  2,4-D could be used to replace MCPA at full tiller wheat.  When radish and broadleaf weeds are small there is very little difference in control between 2,4-D and MCPA.  We also have a new product from Corteva called Quelex.  Quelex is gives us an additional mode of action that will control broadleaf weeds in wheat.  It can be used from the 2-leaf stage through flagleaf and can be tank-mixed with a ryegrass material if needed.

A couple of our products for ryegrass, like Fierce and PowerFlex also provide good control of wild radish.  With all of the formulations and generics it is critical to read and understand the label.  When in doubt call your County Agent for assistance.

One last thing all of these options above should be done prior to you opening any Christmas presents or drinking any egg nog by the fire.

 

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