IPMP3.0, Oregon State University, Copyright 2000

Biology and Management of Barnyardgrass


Registered Herbicides

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General Description:

Barnyardgrass is a summer annual native to Europoe and India.  Vigorous and numerous stems 1 to 5 feet tall with stem bases often red or purple. Flat, wide leaves without a ligule. Panicles are often red or purple. Single plants can produce up to 7,000 seeds.

It prefers wet soils and warm temperatures. These conditions are provided in the summer-irrigated mint fields of the United States. Because barnyardgrass germinated throughout the summer, and because plants can produce new branches and tillers through the season, it is a particularly serious weed in poor or open mint stands.

Impact on Yield:

A barnyardgrass infestation of 32 plants per square foot reduced peppermint oil yield by 37% (Ian Heap).

When both green foxtail and barnyardgrass were present, the peppermint oil yield was suppressed by as much as 32 lbs per acre (Ian Heap).

Herbicide Control Notes:

  • Usually emerges too late for control with Gramoxone. Interference from established mint canopy might limit herbicide coverage and control with later applications of Poast or Assure II. Devrinol is effecitve when application is immediately followed by irrigation or moderate precipitation.