PNW 377 • January 1992 Blackgrass Alopecurus myosuroides Huds. S. Aldrich-Markham Blackgrass (Alopecurus cally because it starts rapid myosuroides Huds.), also growth early in the spring, known as slender foxtail, ranks, competing with the grain for with wild oats and annual resources. In test plots in ryegrass, among the most Washington,DATE. uncontrolled important grass weeds in blackgrass reduced winter winter cereal production in wheat yields by as much as Europe. It infests other winter OF42%, with an average yield crops there as well, including loss of 25%. Most of the grass seed, rapeseed, and abundant blackgrass seeds are forage legumes. shed before the grain is har- vested. Although it’s not yet wide- OUT spread in the United States, it’s been introduced into a number of states, including IS IDENTIFICATION Washington and Oregon. The seedheads of blackgrass There are several infestations Figure 2.—Blackgrass is a are dense and cylindrical, in eastern Washington, in winter annual that may grow similar to those of meadow to 3 feet tall. foxtail (Alopecurus pratensis L.), a perennial species commonly Lincoln,information: Spokane, and planted for pasture in wet Whitman counties. Plants areas (figure 1). have been found within a mile of the Idaho border. The Blackgrass seedheads have a only infestations in Oregon smaller diameter in propor- are in the Willamette Valley, tion to their length than in Yamhill County near the meadow foxtail and are more currentborder with Polk County. tapered at each end. They’re PUBLICATIONBlackgrass has become a usually reddish-purple in serious problem in these color, giving the appearance, areas, where winter wheat is from a distance, of a “black an important crop. It’s listed grass.” The two species are most as a noxious weed in Wash- among the earliest grasses to THIS ington. flower in the spring, blackgrass flowering slightly Because of its extremely high later than meadow foxtail. For seed production capability, Figure 1.—Blackgrass (left) is blackgrass has the potential Blackgrass plants grow up to 3 distinguishdhttp://extension.oregonstate.edu/catalog by the dense, for rapid spread. It’s a winter feet tall (figure 2). The seed- cylindrical seedheads that are annual, and the cultural heads are from 1 to 5 inches practices used for winter more slender and more tapered at Susan Aldrich-Markham, Extension the ends than those of meadow grains suit blackgrass as well. agent, Yamhill County, Oregon State foxtail (right). It can reduce yields dramati- University. A Pacific Northwest Extension Publication • Oregon • Idaho • Washington long and 1⁄8 to 1⁄4 inch in responds to over 30,000 seeds The seeds germinate over a diameter, tapering at each per square foot. At lower wide range of temperatures, end. Each spikelet has a single plant densities, each plant with high germination be- floret, enclosed by two keeled produces more seedheads. tween 48 and 77°F. Germina- glumes of equal length. tion occurs all year long, with Blackgrass seed loses dor- peaks in fall and spring. In The lemma, palea, and glumes mancy within 2 months of winter grains, most of the remain attached to the seed maturity; then it can germi- blackgrass seeds germinate in when it’s shed. The lemma has nate. It can remain viable in the fall. Those emerging in the 1 a bent awn, about ⁄4 inch long, the soil when buried for as spring are likely to be sup- protruding from near the base long as 7 to 9 years. The pressed by crop competition (figure 3). These small, deli- percentage of viable seeds in except in thin or late-planted cate awns give the seedhead cultivated soils, however, stands. the appearance of having declines rapidly when replen- short hairs. ishment with new seeds is Blackgrass plants stop grow- prevented. ing at aboutDATE. 40°F. Tolerance to The leaves are hairless, with cold temperatures depends on an open sheath, and rolled in A researcher in England the stage of development. At the bud. The sheaths can be observed that a 3-year rota- theOF one- to two-leaf stage, green or purplish. There are tion out of cereals into grass plants can survive tempera- no auricles. The ligules are silage (where the blackgrass tures down to 18°F; larger membranous, with a jagged was cut before heading) plants can survive –13°F. Cold edge (figure 4). considerably reduced, but temperature tolerance is didn’t eliminate, viable seedsOUTimproved with good soil from the soil. It didn’t prevent moisture. BIOLOGY a recurrence of blackgrassIS in AND ECOLOGY the following cereal crop, and Blackgrass prefers moist soils. failure to control the weed in It grows most abundantly in The most significant feature of that crop allowed new seeds the low areas of fields and on blackgrass as a weed is its to enter the soil. heavy soils with a high winter high seed production. One water table, but it’s not con- seedhead commonly produces fined to these areas. 100 to 200 seeds. A researcher information: in England found an average Native to the Mediterranean of 1,550 seedheads per square region, blackgrass is now a meter in wheat fields major problem in Germany, under reduced Belgium, France, and Great tillage. This cor- Britain, as well as parts of Italy, Yugoslavia, and Turkey. current Its spread through Europe has PUBLICATION been tied to the expansion of winter wheat and barley acreage, under modern, mechanized cultivation. most There are several factors in THIS modern grain production that have favored the spread of For blackgrass in Europe: • The suppression of most http://extension.oregonstate.edu/catalogbroadleaf weeds with Figure 3.—Left: Seed enclosed by herbicides has favored grass glumes. Right: Seed and lemma weeds such as blackgrass with awn (glumes removed). by reducing competition. 2 used in combination with chemical control, because even a partial failure of chemical control will allow a rapid weed buildup. Rotation out of winter grain to a spring crop or a perennial crop is effective in reducing infestations. Tillage for a spring crop will kill fall- germinated blackgrass. In perennial crops, the blackgrass seedlings have difficulty competing with existing vegetation.DATE. Delaying fall planting of grain allows more weed seedlings to emerge, OFwhich are then destroyed by tillage. Reduced tillage systems favor blackgrass. Surface tillage OUT creates an ideal seedbed for the weed, but when grain is drilled directly into straw IS from the previous year (no- till), the heavy residue inhibits blackgrass establishment. Figure 4.—Ligule, front and side views. Center: leaf tip. The most effective practice for reducing infestations is plow- information:ing, which buries the seed and • The deterioration of soil • Distribution of contami- reduces the number of seed- structure caused by com- nated cereal seed has also lings that can germinate. In paction from heavy equip- contributed to the spread of England, a study of blackgrass ment and by reduction of this weed. populations under different soil organic matter has cultivation systems showed created a favorable environ- PREVENTION that, after 4 years with no ment for blackgrass, whichcurrent grass herbicide: thrivesPUBLICATION in heavy, moist soils • Plant certified seed. • tine-cultivated wheat fields and tolerates poor drainage. • Rogue or destroy new averaged 1,550 seedheads • Blackgrass responds well to infestations. per square meter; high nitrogen fertilization • Clean equipment, especially • direct-drilled fields aver- with increasedmost tiller and combines. aged 850; and THISseed production. • Cut infested areas last or • plowed fields averaged 110. • Using combines for harvest- separately. Foring favors the dispersion of The infestations increased seeds—60 to 90% of the CONTROL under all cultivation systems. seeds are shed by the time In fields where straw was of harvest,http://extension.oregonstate.edu/catalog and the rest are CULTURAL. A high level of burned instead of baled, the spread over the field with control is needed to prevent blackgrass populations were the chaff. an increase in blackgrass seed lower, but they still gradually reserves in the soil. Cultural increased. control practices need to be 3 CHEMICAL. Grain growers herbicides and changes in in Europe find that an annual permissible herbicide prac- control program using grass tices, this publication doesn’t herbicides is necessary to make specific herbicide rec- prevent blackgrass popula- ommendations. tions from increasing. Control in the early stages of growth is For current recommendations, important because blackgrass refer to the Pacific Northwest competes with the grain Weed Control Handbook, pub- during the period of early lished and revised annually by spring growth—and it can the Extension Services of seriously reduce yield. Oregon State University, Washington State University, Populations of blackgrass and the University of Idaho. resistant to the herbicide diclofop-methyl (Hoelon) In addition, detailed instruc- DATE. have been documented in tions for herbicide use are Great Britain. provided on herbicide con- tainer labels and in other OF Since herbicide registrations literature provided by herbi- change frequently, resulting in cide manufacturers. more or fewer available OUT IS information: currentFigures 1 and 2 are by the author. Figure 3 is reproduced, with permission, from Ernst PUBLICATIONHäfliger and Hildemar Scholz, Grass Weeds 2 (Basle, Switzerland: Documenta CIBA- GEIGY, 1981); 1981 by CIBA-GEIGY Ltd. Figure 4 is reproduced, with permission, from C. Leo Hitchcock, Arthur Cronquist, and Marion Ownbey, Vascular Plants of the Pacific Northwest, Part 1: Vascular Cryptogams, Gymnosperms, and Monocotyledons, Publications in Biology vol. 17 (Seattle: University of Washington Press, 1990); 1969 by most University of Washington Press. THIS Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the Oregon State University Extension Service, O.E. Smith, director; Washington State University Cooperative Extension, Larry G. James, interim director; the University For of Idaho Cooperative Extension System, LeRoy D.