Pest Information
Common Name: Quackgrass
Family Name: Poaceae
Latin Name: Elytrigia repens (Agropyron repens)
Other Names: couch grass,medusa's head, Quackgrass rye, Twitch.
Provincial Designation: Common
Life Cycle: Annual
Mode of Spread: Seed, Vegetative

Detailed Information
Description: A cool-season, perennial grass that grows 0.75 m or more laterally from the main shoot before sending, aerial stems. The leaves are flat and slightly hairy on the upper surface. There are clasping auricles at the base of the leaf blade. The spikelets have 3 to 7 florets, attached broadside to the flowering stem. There are 2 horizontal rows on each spike. The seed is narrow and straw-colored at maturity. The rhizomes are white with brown bracts and pointed tips.
Growth and Development (Life Cycle): Emergence: Seedling germinate and rhizome buds start growth at the soil temperatures greater than 5 degrees C. Soil temperature of 5 to 15 degrees C favor shoot growth. While growth is stopped completely at 40 degrees C, however, this condition rarely occurs in Alberta. Recovery of quackgrass is poor at higher temperature, so this is a good time for control operation. The long days of spring favors rhizome development.
Seed Production: Production of viable seed is low and spread by seed is minimal.
Seed germination: Quackgrass seed germinate at temperatures between 5 to 30 degrees C and does not require after ripening period to germinate. It does not require temperature fluctuation to germinate. This temperature favors germination during most of the growing season with the exception of July and early August when conditions tends to be too dry in most of the Alberta.
Longevity in the soil: Buried seed may lie dormant for two to three years and retain its viability for four to five years.
Dispersal: wind
Reproduction (Dispersal): Seed: Quackgrass is wind-pollinated but self-sterile. Production of viable seeds requires cross-pollination from genetically different clones. This is main reason why viable seed production is low and spread by seed is minimal. Moreover forage seed contaminated even with few quackgrass seeds may not only infest clean land, but may also introduce generically different clone to the areas previously occupied by a single clone and so make seed production possible.
Roots/Rhizomes:the creeping underground stem is called the rhizome, is the main mode of reproduction. Each bud on the rhizome is capable of producing new shoot, if stimulated as by tillage or digging. Dormant buds can produce new shoots through cultivation and by mowing above ground parts. Most rhizomes are in top 10 to 15 cm of soil.
Some facts about quackgrass rhizomes:
  • In one year, a plant produced from a single bud can spread to 3 m in diameter; produce 135 new rhizomes and produce 206 new shoots.
  • Long days favors rhizomes development
  • High light intensity in open fields favors rhizome development
  • Soil temperature of 5 to 15 degrees C favors rhizome development
  • Frost only kills rhizomes at the soil surface
  • Economic Importance (Beneficial Aspects): Detrimental: Quackgrass compete strongly with small grains and forage crops. The value of grass seed crops may be greatly reduced if contaminated with quackgrass seeds. Quackgrass serves as an alternative host plant for many plant pathogens.
    Beneficial: Quackgrass may be used for pasture or hay. Crude protein of quackgrass is comparable with timothy at the same stage of growth. Quackgrass roots and rhizomes are effective soil binders on the slopes, embankments and sandy soils. It provides cover for wildlife, including small mammals.
    Flowering: Flowering timing: flowering and seed production occurs in June and early July in grasslands and direct seeded fields. Seed ripens late July or early August. Several tillage operations will delay flower and seed set
    Yield Losses: Quackgrass is a strong competitor with crops for several reasons. First, it can maintain a high growth rates in cool weather. Second, quackgrass can tie up a large percentage of N, P, and K from the soil and make them unavailable to crop. Third, this weed reproduces easily from rhizomes and may contain toxin that inhibit growth of crop. In trials conducted near Vegreville, Alberta, 50 and 100 shoots/m2 reduced canola yields by 18 to 32 per cent. In barley, 60 to 100 shoots/m2 reduced barley yields by 40 to 50 per cent (O’Donovan 1987, 1990). The economic threshold in canola is about 20 to 25 shoots/m2

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    Last Modified: February 03, 2009

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