Scientific names: Lolium multiflorum, previously Lolium italicum
Other names: annual ryegrass, Australian rye
Italian ryegrass (Lolium multiflorum) is a problem in grain systems in NYS. It is a winter annual that is used as a cover crop, but it can be difficult to remove during the termination period . It originated in southern Europe and grows well in various soils, but favors well-drained and productive soil conditions. It is not winter hardy.
Note: there is another grass species that is commonly referred to as “annual ryegrass” and is in the same genus, Lolium, as L. multiflorum. Therefore, close attention to identification characteristics between these species should be considered when distinguishing between L. multiflorum (common names: annual ryegrass, Italian ryegrass, and Australia rye) and L. rigidum (common names: annual ryegrass, rigid rye). See the similar species table below for clarification. Also, rigid rye was the first within the Lolium genus to develop resistance to multiple pesticide groups of action, which is a pattern for the ryegrass species.
Italian ryegrass as corn cover crop.
Photo by Alan Manson, via Wikimedia.org
Similar species
Table 11: Compares ryegrasses: Italian and perennial ryegrasses (Lolium multiflorum and Lolium perenne) and quackgrass (Elytrigia repens).
| Species | Italian ryegrass (Lolium multiflorum) | Perennial ryegrass (Lolium perenne) | Rigid ryegrass (Lolium rigidum) | Quackgrass (Elytrigia repens) |
|---|---|---|---|---|
| Similarities | Leaf bud rolled; ligule membranous; no auricles; smooth or occasional hairs on blades and lower sheath | Leaf bud rolled; ligule membranous; no auricles | Leaf bud rolled; small narrow auricles; annual like Italian ryegrass | Awns and seed heads looks like ryegrass species |
| Differences | Annual; taller than perennial ryegrass maximum height of 3 ft (1 m) and grows more vigorously; auricles are long and clasping, like claws; awns present; one basal bract; | Perennial; shorter than Italian ryegrass (12-24 in or 30-60 cm); auricles are small or malformed; awns are absent or reduced; one basal bract | Difficult to tell apart between Italian and rigid ryes as seedling; at maturity rigid rye has no awns; | Perennial; produces rhizomes; two basal bracts |
Identification
Multiple seedlings of Italian ryegrass.
Photo by andreasbalzer, via Flicker.com
Leaf and collar region of Italian ryegrass.
Photo by Forest and Kim Starr, via Flicker.com
Mature Italian ryegrass.
Photo by Krzysztof Ziarnek, Kenraiz, via wikimedia.org.
Two flower heads of Italian ryegrass.
Photo by Harry Rose, via Flicker.com
Italian ryegrass spikelets.
Photo by Harry Rose, via Flicker.com
Management
Chemical
When planted in the fall or winter wheat systems, Italian ryegrass can be managed using group 9 and 22 herbicides, such as glyphosate and paraquat.
You can also use CEE Eastern NY Horticulture’s herbicide lookup tool to find the efficacy of various herbicides on a Italian ryegrass. For general guidance on weed control, get the latest edition of the Cornell Crop and Pest Management Guidelines.
Non-chemical control
In hot weather, L. multiflorum grows poorly. A rotation between winter grains and summer row crops disrupts the life cycle of L. multiflorum. Summer row crops can help control this grass if tine weeding, inter-row cultivation and hilling up of crops are used. If tilling is used, seeds are buried, which helps to suppress the population. The seeds die quickly, and need to be near the surface to emerge, so plowing can provide longer term control. Italian ryegrass can be used as a forage crop if all other control fails, which will cause a good portion of seed to be damaged and inhibit germination. This species can be used as a cover crop; however, this should be avoided in areas where it is a problem or could become one. Plastic and organic mulches effectively suppress this grass.
Natural enemies
This species does have some natural enemies, including mites, crown rust, gray leaf spot, stem rust, and ryegrass blast.
Climate Change and Management
Perennial ryegrass is particularly vulnerable to heat events, becoming less competitive, especially against C4 grasses such as corn. While dense growth provides some heat tolerance, perennial ryegrass is likely to become less common in sparsely vegetated areas as heat events become more common, potentially leading to bare ground and opportunities for other weeds to colonize.
# of studies referenced in this section: 1
Herbicide resistance
Reported as of 2021:
North America
U.S.
Groups 1 (7 states), 2 (3 states), 9 (4 states), and 15 (2 states)
2-way multiple resistance to groups 1 and 2 (Missouri)
2-way multiple resistance to groups 1 and 2 (NC, SC, GA)
2-way multiple resistance to groups 9 and 10 (OR)
4-way multiple resistance to groups 1, 2, 9, 22 (CA)
Other continents
Asia
Group 9
Australia
4-way multiple resistance to groups 1, 9, 10, and 11 (New Zealand)
Europe
Groups 1, 2, 7, 9, 15
2-way multiple resistance to groups 1 and 2 (Denmark, France)
3-way multiple resistance to groups 1, 2, 9 (Italy)
South America
2-way multiple resistance to groups 2 and 9 (Argentina)
3-way multiple resistance to groups 1, 2, and 9 (Brazil and Chile)
For a more detailed report, please visit the reference section below or visit the International Herbicide-Resistant Weed Database homepage for more information on resistance.
References
For more information please look for the upcoming book, Manage Weeds on Your Farm: A Guide to Ecological Strategies by Charles L. Mohler, John Teasdale, and Antonio DiTommaso (Publisher: SARE Outreach, expected late fall of 2021).
Washington State University has a profile on Italian ryegrass that describes the species ID characteristics and control methods.
Uva R H, Neal J C, DiTomaso J M. 1997. Weeds of the Northeast. Book published by Cornell University, Ithaca NY. The go-to for weed ID in the Northeast; look for a new edition sometime in 2019.
Cornell University has a page discussing the conditions for ryegrass (or ‘rye’) as a cover crop with control recommendations
For a comparison between Italian ryegrass and perennial ryegrass check out this UC IPM page.
This Q&A from Cornell University addresses ryegrass poisonings in livestock.
For general guidance on weed control, get the latest edition of the Cornell Crop and Pest Management Guidelines. Since this species is generally problematic in Field Crops, you may be interested in the Guidelines specific to those crops.
For more information on rigid rye consider look at CABI’s Invasive Species Compendium.
Bararpour, M. T., Norsworthy, J. K., Burgos, N. R., Korres, N. E., & Gbur, E. E. (2017). Identification and biological characteristics of ryegrass (Lolium spp.) accessions in Arkansas. Weed Science, 65(3), 350-360.
Herbicide resistance details
North America
U.S.
Mid-West: Michigan, groups ; Kentucky, group 2 (mesosulfuron-methyl, and pyroxsulam); Missouri, multiple resistance to groups 1 and 2 (mesosulfuron-methyl, and pinoxaden)
South East: North Carolina, multiple resistance to groups 1 and 2 (diclofop-methyl, imazamox, mesosulfuron-methyl, pinoxaden, pyroxsulam, and sethoxydim), and group 9 (glyphosate); South Carolina, multiple resistance to groups 1 and 2 (diclofop-methyl, mesosulfuron-methyl, and pyroxsulam); Tennessee, group 1 (diclofop-methyl) and 9 (glyphosate); Arkansas, groups 1 (clodinafop-propargyl, diclofop-methyl, and pinoxaden) and 9 (glyphosate); Louisiana, group 9 (glyphosate); Georgia, multiple resistance to groups 1 and 2 (diclofop-methyl, and mesosulfuron-methyl); Mississippi, group 2 (sulfometuron-methyl)
North West: Idaho, group 1 (clodinafop-propargyl, diclofop-methyl, quizalofop-ethyl, and sethoxydim); Oregon, group 1 (diclofop-methyl) and 15 (flufenacet), and multiple resistance to groups 9 and 10 (glufosinate-ammonium, and glyphosate); Washington, group 15 (flufenacet)
Mid-Atlantic: Delaware, group 2 (mesosulfuron-methyl); Maryland, group 1 (diclofop-methyl); Virginia, group 1 (diclofop-methyl)
South West: Oklahoma, group 1 (pinoxaden)
West: California, multiple resistance to groups 1, 2, 9, 22 (glyphosate, glufosinate-ammonium, paraquat, sethoxydim, clethodim, cyhalofop-butyl, fenoxaprop-ethyl, fluazifop-butyl, imazamox, mesosulfuron-methyl)
Other continents
Asia
Japan, groups 9 (glyphosate)
Australia
New Zealand, multiple resistance to groups 1, 9, 10, and 11 (haloxyfop-methyl, pinoxaden, amitrole, glufosinate-ammonium, glyphosate)
Europe
Denmark, multiple resistance to groups 1 and 2 (clodinafop-propargyl, florasulam, iodosulfuron-methyl-Na, mesosulfuron-methyl, and pyroxsulam); France, multiple resistance to groups 1 and 2 (clodinafop-propargyl, diclofop-methyl, flupyrsulfuron-methyl-Na, haloxyfop-methyl, iodosulfuron-methyl-Na, mesosulfuron-methyl, propoxycarbazone-Na, and sethoxydim), also group 15 (flufenacet); Italy, multiple resistance to groups 1, 2, 9 (clodinafop-propargyl, cycloxydim, diclofop-methyl, iodosulfuron-methyl-Na, mesosulfuron-methyl, pinoxaden, sethoxydim, tralkoxydim, glyphosate, and quizalofop-ethyl); Spain, group 9 (glyphosate); Switzerland, group 9 (glyphosate); United Kingdom, groups 1 (cycloxydim, diclofop-methyl, fluazifop-butyl, pinoxaden, and tralkoxydim), 2 (mesosulfuron-methyl and pyroxsulam), 7 (isoproturon), and 15 (flufenacet)
South America
Argentina, multiple resistance to groups 2 and 9 (glyphosate, iodosulfuron-methyl-Na, and pyroxsulam); Brazil, multiple resistance to groups 1, 2, and 9 (clethodim, glyphosate, iodosulfuron-methyl-Na, and pyroxsulam); Chile, multiple resistance to groups 1, 2, and 9 (flucarbazone-Na, glyphosate, glyphosate-trimesium, iodosulfuron-methyl-Na, clethodim, clodinafop-propargyl, diclofop-methyl, pinoxaden, tepraloxydim, haloxyfop-methyl)