Glyphosate-resistant ryegrass is gaining traction in Alabama fields, says Steve Li, weed specialist with Alabama Cooperative Extension.
The herbicide-resistant ryegrass problem is particularly growing in no-till and strip-till fields. In the April 13 Alabama Extension Cotton Shorts Newsletter, Li provided some guidance on managing resistant ryegrass for 2021 along with some telling pictures of a study he is conducting to address the issue.
- Refrain from planting ryegrass as a fall cover crop. Some growers in Alabama spread ryegrass seeds after harvest for use as a cover. This always make me nervous! Seeded ryegrass can evolve resistance to herbicides just like wild populations. There is no guarantee that purchased ryegrass seeds are totally “herbicide resistance free.” You might be planting your own resistant ryegrass seeds without even knowing it.
- Kill ryegrass before seed heads emerge. This prevents ryegrass seed production and elimnates the chance to pass down herbicide resistance to the next generation.
- Once a few ryegrass patches appear that you cannot kill with glyphosate, always use Gramoxone and clethodim to control them. Do not let resistant populations fully establish on your farm; they will be hard to get rid of thereafter.
Select Max 12 oz + Crop oil + AMS 2 lb/A followed by Gramoxone 2lb @ 32 oz + Crop oil + AMS 2 lb/A 7 days later. 100% control of ryegrass at seed head stage. Photo courtesy of Steve Li.
Gramoxone 2lb @ 32 oz + Select Max 12 oz + Crop oil + AMS 2 lb/A. One pass program. Greater than 95% ryegrass control at seedhead stage. Photo courtesy of Steve Li.
There have been multiple reports from the Mississippi Delta and North Alabama regarding ryegrass resistance to clethodim. We do not want to put too much selection pressure on clethodim and lose its efficacy on ryegrass in the near future. If ryegrass pressure is very high, consider an application of Warrant, Zidua or Dual Magnum in early November when ryegrass is germinating.
The study is part of a larger-scale study funded by the Alabama Cotton Commission to address winter and summer grass control.