What is in this article?:
- A typical Mississippi Delta winter is the ideal environment for Italian ryegrass.
- Italian ryegrass thrives where there are mild climates and fertile soils. It has a low tolerance for both hot, dry climates and harsh winter conditions. The generally mild winter temperatures and rich soils in the Delta provide a perfect niche for Italian ryegrass.
- Italian ryegrass plants also grow rapidly. The extended emergence window and rapid growth complicate herbicide programs targeting this weed.
- A single Italian ryegrass plant can produce 45,000 seed, which is more than enough seed to turn an isolated problem into a train wreck in one or two years.
- Seven Mississippi Delta counties contain populations of Italian ryegrass with multiple resistance to glyphosate, ACCase inhibitors, and ALS inhibitors.
Mississippi wheat crop
A sizeable wheat crop is presently up and growing in Mississippi. If you have wheat planted in one of the seven counties listed above, be mindful of your weed pressure. There is a good possibility that if you have Italian ryegrass, you may not be able to control it with Hoelon, Osprey, or PowerFlex. If this is the case, then the only remaining postemergence herbicide option at your disposal is Axial XL, and it may only be applied once per crop season.
In addition, if you have wheat, and are outside the above counties, do not assume the Italian ryegrass in your fields is not resistant to these herbicides.
In my wheat trials at Stoneville, I have produced excellent wheat yields when using a single application of Axial XL at spring green up. However, I rarely achieve 100 percent Italian ryegrass control with Axial XL applied in the spring.
The surviving Italian ryegrass plants produce seed that can be spread by the combine. These plants may not produce 45,000 seed growing in competition with wheat and following a herbicide application, but the seed that are produced will be there next year and will have to be managed at that time, either in wheat or during burndown.
So, Italian ryegrass plants not controlled in wheat contribute to a vicious cycle that must be broken in order to get ahead of this problem.
Herbicide resistance is on everyone’s mind. In areas with severe infestations of Palmer amaranth and Italian ryegrass, it is a never-ending grind because the growing seasons for these weeds only slightly overlap. Just because Italian ryegrass does not emerge and grow at the same time as row crops does not lessen its impact.
Be attentive. Scout for Italian ryegrass. We still have some effective herbicides to manage this weed in the burndown arena if they are used correctly in a program.
Our weed science group at Mississippi State has developed a one-page document listing programs for managing glyphosate-resistant Italian ryegrass during burndown (http://msucares.com/crops/weeds/index.html). If you have any questions about these programs, feel free to contact me at (662) 820-7794.