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     Wednesday, August 27, 2014

(Setaria viridis)

OTHER NAMES: Bottle grass, green bristle grass, wild millet, pigeon grass.

ORIGIN: Europe

HABITAT: Grain fields, gardens, roadsides and waste places.

DESCRIPTION: Annual, reproduction by seed.

STEM: Erect, branching at the base, 20-60 cm tall.

LEAVES: Flat, without hairs, rough, pointed blade five to 25 cm long.

HEADS: Cylindrical, tapering toward the summit, 2.5-10 cm long, soft, bristly, green.

SEEDS: Whitish, pale yellow or purplish, 1.5 mm long. About 350-450 seeds/head produced.

Green foxtail is a heavy seed producer but is a poor competitor unless in dense stands. It is slower germinating grows rapidly, and can compete with the crop. Under low light intensity green foxtail plants grow very poorly and remain small.

The seeds have some dormancy which is lost in a few weeks under cool, moist conditions and more slowly under warm, dry conditions.

CULTURAL CONTROL PRACTICES:

Temperature, depth of burial and dormancy play an important role in the control of germination and emergence of green foxtail.

Germination occurs readily at temperatures from 15 degreed celsius to 35 degrees celsius which occur mainly during late May and early June. However, germination may continue up to September with the main flush of growth in June and subsequent germination associated with the occurrence of rainfall.

Most seedlings emerge from depths of 1-2.5 cm. Deep burial of the seeds influences their survival in the soil. Therefore, summerfallow tillage should be shallow to initiate germination. Maintaining a firm seedbed will also encourage germination of the seed.

Green foxtail is a poor competitor under most circumstances and can be controlled by strong crop stands produced with the aid of early seeding and good fertilization. Barley and rapeseed rank as the most efficient competitors against green foxtail. Spring rye, oats, wheat and flax have a lower ranking and row crops are generally poor competitors. However, green foxtail can result in significant yield losses if it emerges ahead of or with any crops planted.

Crop varieties are also important to consider. In wheat, it was discovered that a semi-dwarf variety was more susceptible to foxtail competition than normal height varieties. Early maturing varieties can compete either by effectively shading out the foxtail or by advancing through its critical period of early growth before the onset of severe foxtail competition. This will not eliminate foxtail since the suppressed plants may still produce sufficient seed to ensure a substantial infestation in the following year.

Because foxtail requires warm soil temperatures for germination, it usually escapes spring cultivation for weed control. For this reason, delayed seeding is not suitable for control. To effectively reduce foxtail competition, a competitive crop should be sown as early as possible, and at a slightly higher seeding rate to provide a dense stand which will out-compete the weed.

Harrowing will also help to control green foxtail. This can be done either as a pre-emergent harrowing should be done before crop sprouts are 2.0 cm long. Wheat and barley crops can be harrowed after emergence if the topsoil is relatively dry. There should be no yield reduction unless the wheat is harrowed a the 1-1 1/2 leaf and the barley at the 2 1/2-3 leaf stage.

A build-up of green foxtail is believed to be hampered by summerfallow. Summerfallowing every third year helps to prevent excessive increases. However, except in low rainfall areas where fallowing helps conserve soil moisture, it is difficult to justify the practice solely as a means of controlling weeds.

Forage crops provide competition. These should be left down for at least three years as green foxtail seldom lives more than three years in the soil.

CHEMICAL CONTROL PRACTICES:

Please refer to Saskatchewan Agriculture's Guide to Crop Protection for current herbicide rates and application recommendations.

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