IPMP3.0, Oregon State University, Copyright 2000

Biology and Management of Italian Ryegrass


Registered Herbicides

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Italian Ryegrass

General Description:

Italian Ryegrass is a highly competitive winter annual. It has become a serious pest in many peppermint fields West of the Cascade Mountains. Erect stems often purplish at base and 1 to 2 1/2 feet tall. Shiny, dark green leaves have prominent veins. Long spikes have spikelets that are alternate along the stem.

Impact on Yield:

Its highly competitive nature, coupled with its propensity to develop resistance to herbicides, makes Italian ryegrass a particlularly troublesome weed in mint.

Peppermint oil yields have been reduced by as much at 50 lbs per acre.  Even after a 73% reduction in the Italian ryegrass infestation, the yield was reduced 23 lbs per acre (Ian Heap).

Herbicide Control Notes:

  • Gramoxone plus Sinbar, Goal, or Karmex/Direx usually is effective on small Italian ryegrass. Herbicide-resistant Italian ryegrass is widespread in western Oregon. Poast, Assure II, Karmex/Direx, and Sinbar often not very effective when used individually.