Italian Ryegrass Management

Italian ryegrass is a problematic weed for many Midsouth soybean producers, and when uncontrolled, can significantly reduce soybean yields. Its control is difficult, and is hampered by the weed’s development of resistance to several classes of herbicides [Heap, 2024] that include WSSA Groups 1 [ACCase inhibitors], 2 [ALS inhibitors], 9 [EPSP synthase inhibitor], 10 [glutamine synthetase inhibitor], and 15 [VLCFA inhibitors]. Click here for a list of herbicides in each class or group.

The following points provide producers the best options for managing this troublesome weed.

Time of year to treat for best control. Since this weed is a winter annual that comes up from seed each year, the best time to treat it is in the fall with an application of a residual herbicide to prevent its emergence. Producers should start checking the 10-day weather forecast on about Oct. 15 to ensure there is a high probability of rainfall that is needed to activate the residual herbicide that is applied.

Size of weed to treat. Postemergence [PE] herbicide applications that are made for spring burndown of this weed should be made when it is no taller than 4-6 in.

Other points to consider are:

•   Never use Italian ryegrass as a cover crop.

•   Repeated use of herbicides with the same mode of action should be avoided.

•   Producers should read the label of a chosen herbicide to be aware of crop rotation and/or plant-back restrictions that may be associated with that herbicide. Click here for Univ. of Ark. Publication MP519 that provides a crop replant and rotation guide for soybean herbicides, and here for pages 43-44 of Univ. of Ark. Weed Control Guide MP44 that contains a crop replant and rotation guide for soybean herbicides.

•   Complete control of Italian ryegrass will likely require the application of a spring burndown herbicide following fall control measures that may include one or more tillage operations.

•   Relying on PE herbicides alone to control this weed is not recommended.

The following resources provide detailed information regarding the control of this troublesome weed in soybeans.

•   Italian Ryegrass Management in Soybeans–USB TakeAction

•   Management of Italian Ryegrass in Agronomic Crops–Univ. of Ark. FSA2191

Composed by Larry G. Heatherly, Oct. 2024, larryh91746@gmail.com