Weed of the Week: Italian Ryegrass

Jason Bond, Research/Extension Weed Scientist
By Jason Bond, Research/Extension Weed Scientist September 10, 2012 10:39 Updated

Written by Aly Shinkle, Jason Bond, and Tom Eubank

Italian ryegrass
Family:  Poaceae
Scientific name:  Lolium perenne ssp. multiflorum (L.)
Synonyms:  Annual ryegrass, ryegrass

Diagram courtesy of Dr. Charles Bryson

Italian ryegrass is an erect, winter annual grass that can reach up to 4 feet in height with narrow leaf blades from 3 to 15 inches in length.  The ligule is a short, flat membrane, and auricles (finger-like appendages) are present at the leaf collar.  Plants will have no hairs and will display a glossy, dark green coloration due to the waxy surface of leaf blades.  The seedhead is a spike containing 5 to 38 spikelets.  Italian ryegrass can be distinguished from other winter annual grasses such as downy brome (Bromus tectorum) and cheat (Bromus secalinus) by its lack of hair and from annual bluegrass (Poa annua) by the presence of the auricles at the leaf collar.  Plants germinate from fall through early spring, are highly competitive, and grow rapidly in the winter and early spring months.

Seedling Italian ryegrass

Italian ryegrass is native to Europe but it can be found throughout the United States and Canada.  In Mississippi, Italian ryegrass is problematic in fields, pastures, lawns, turf, and roadsides and has evolved resistance to glyphosate, ACCase-inhibiting (Hoelon, Fusilade, Assure II), and ALS-inhibiting (Accent, Osprey, PowerFlex, Resolve) herbicides.  Thirty-two counties in Mississippi contain populations of glyphosate-resistant Italian ryegrass. Problematically, Italian ryegrass emerges from fall through early spring, making it difficult to control with a single herbicide application.  Best control in fallow fields is achieved with residual herbicides (Boundary, Command, Dual Magnum, or Treflan) in the fall followed by postemergence treatments (clethodim or paraquat) targeting escapes in early spring.  In wheat, Italian ryegrass should be managed with an early-season application of Axiom followed by spring application of Axial XL.  Furthermore, Italian ryegrass hosts endophytic fungal toxins which can cause disorientation and negative health effects in grazing animals, complicating pasture and forage management.

Bryson, C.T. and M.S. DeFelice. 2009. Weeds of the South. Athens, GA: University of Georgia Press. pp. 390

Italian ryegrass with glossy, dark green color

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Jason Bond, Research/Extension Weed Scientist
By Jason Bond, Research/Extension Weed Scientist September 10, 2012 10:39 Updated
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