We’ve had 3/10″ of rain so far with the cold front. This is really going to help our grazing crops get going. One thing we need to think about now is weed control. UGA Extension Weed Scientist Dr. Stanley Culpepper says we need to get our weed control done by Christmas. Once we get to February, it’ll be too late to manage ryegrass and wild raddish with herbicides. We look at weed control a little different between small grain production and grazing.
Small Grain Weed Control
Use of Harmony for broadleafs has a large window for safe application, but do not apply 2,4-D to small grain that is not fully tillered. Also, do not apply 2,4-D after small grain is jointing.
Below is a list of most effective wheat program from Dr. Stanley Culpepper:
- Harmony TS followed by MCPA or 2,4-D
- Harmony TS + MCPA or 2,4-D
If you have early emerging small grain with weeds, the first program is your only option. If you have later emergence, and few emerged weeds, you can go with the second program. Keep in mind, we need to be above 50 degrees when treating. The sooner you apply before cold weather the better.
In terms of genetic stability, ryegrass is worse than pigweed. For control of ryegrass, it is important that each field is treated only once every two years with the respected chemistry. For instance, if we use Axial this year, we do not spray Axial or Hoelon on that piece of ground next year at all. The same applies to Powerflex and Osprey. If we do not rotate, we will lose the chemistry. Below is a graph of these chemical classes:
Forage Weed Control
The biggest difference in our grazing and small grains is that we are not worried about yield, only biomass. Therefore, we can be more relaxed with our timing. Instead of having 5 – 6 tillers, we can use MCPA or 2,4-D at just a few tillers. Remember, oats are less tolerant of 2,4-D than wheat. In grazing oats, we can treat at 3 tiller.
UGA Extension Weed Scientist Dr. Culpepper says, “Treating oats with 3 tillers should not reduce biomass production but could influence seed production.”
What is full tiller? Following emergence and the spike stage, small grain crops begin to tiller. These are essentially stems that will produce a grain head in the future. When we have 5 or 6 tillers on a plant, it is considered full tiller. Depending on growing degree days, it will generally take between 20 and 35 days to reach full tiller.
With the same herbicides, we don’t want to treat once crop enters the jointing stage. Just before jointing, the stems will elongate. At the base of the stem, you will feel a swelling of the stem (almost like a bee bee inside the stem) which is the first node or joint. The joint is the growing point. The plants have now moved into the reproductive growth stages.