||In Alberta, downy brome has become a serious weed on rangelands, winter wheat, alfalfa, grass-seed fields, pasture land and non cropland.
Frequency, density and ranking of downy brome in Alberts
|Agricultural Ecoregion||Frequency1 (%)||Density2 (%)||Ranking|
|Moist Mixed Grassland||0.1||0.4||73|
|Peace Lowland|| || || |
|Alberta (All regions)||0.2||4.2||70|
1 Frequency: Percent of fields in which hawk’s-beard occurred2 Density = Average number of hawk’s-beard in occurrence fields.
Source: Leeson 2005 (Prairie Weed Survey 1970s to 2000s)
||An erect winter annual, spring annual, or biennial herb, which often grows in tufted, clumps. Stems are erect and slender with a finely divided fibrous root system. Leaf blades are flat and hairy. The inflorescence is a dense, drooping panicle 1 ½ to 8 inches long and is pale green to purplish in color. Branches are thin, flexuous, and pubescent. Spikelets are four to seven-flowered and pubescent or villous.
|Growth and Development (Life Cycle):
||Emergence: Downy brome seedlings usually germinate in the late summer or autumn, after first fall rain when soil temperature is about 20 degrees C. The fall-germinated seedlings often over-winter in a semi-dormant state and complete their lifecycle the following spring (Upadhyaya et al. 1986).
Seed Production: Downy brome is a prolific seed producer and is capable of producing up to 400 lbs. of seeds/acre (Upadhyaya et al. 1986).
Seed germination: Seeds germinate at or near the soil surface over wide range of soil temperature and moisture conditions, with most of the seeds germinating within a year of maturation. The seed matures in mid to late June and shatters within a week of maturity (Upadhyaya et al. 1986). In minimum tillage systems seeds can remain viable up to 3-4 years if they are deposited on heavy residue.
Dormancy: Under adequate moisture conditions, the majority of downy brome seeds will germinate in the fall, or within a year of maturation (Upadhyaya et al. 1986). However, dry conditions can cause environmentally induced dormancy, which may last several years and break down at erratic intervals (Young and Evans 1985).
Longevity in the soil: In minimum tillage systems seeds can remain viable up to 3-4 years if they are deposited on heavy residue.
Dispersal: Downy brome seeds shatter at maturity. Seeds are dispersed short distances by wind, and the long awns can attach to the fur or feathers of an animal, as well as clothing of human beings.
|Economic Importance (Beneficial Aspects):
||Detrimental: Downy brome has become a serious weed on rangelands, winter wheat, alfalfa, grass-seed fields, pasture land and non crop land. In winter wheat it has the potential to cause serious yield losses. Downy brome densities of 108 – 538 plants M-2 reduced winter wheat yield by 40 and 92% respectively. On the pasture and rangelands it crowds out native grasses; and creates wildfire hazards. At maturity the long stiff awns can injure grazing animals by working into the nose, ears, mouth, or eyes.
Beneficial: In a seedling stage, downy brome is an important forage species in the Northwest region of the USA.
||Introduced accidentally through contaminated shipments in 1860s
||Type of Flower: Lacks petals and sepals and consists of three stamens and a single ovary topped by tow feathery stigmas.
Time of Flowering: May - June
|How to Control:
||Integrated Weed Management
Controlling Downy Brome in Adjacent Areas: Downy brome spreads into fields along field borders or fence lines and should be controlled when first observed. Crop management practices, such as banding rather than broadcasting nitrogen, and the quick establishment of a competitive crop, help to control the spread.
Maximizing Seed Germination: Downy brome seeds remain viable for three to four years. Fall harrowing may stimulate more seeds to germinate by increasing soil to-seed contact. These plants can then be controlled in late fall or early spring to help reduce the seed bank.
Managing Crop Residues: Good chaff spreading is important because it evenly distributes downy brome seeds in the field. This helps to prevent the formation of dense, sod-bound patches of downy brome, which can be difficult to control with tillage or herbicides.
Crop Rotation: Restricting winter wheat or fall rye to once every three to four years helps to keep downy brome at low infestation levels. Rotating fall crops with spring crops is advised because downy brome can be controlled with a pre-seeding herbicide application or tillage before spring seeding.
Using Certified Seed: Small grains and grass seeds are often contaminated with downy brome seed. Planting clean seed reduces the risk of re-infestation.
Using Optimum Seeding Dates: Use the optimum seeding date for the area to get early establishment of winter wheat or fall rye. In light to moderate downy brome infestations, a crop emerging before the weed can significantly reduce yield losses.
Maintaining a Good Vigorous Crop Stand: A healthy crop has a competitive advantage over downy brome.
||Spring Pre-seeding Weed Burndown Application: In direct seeding system, downy brome can be controlled in the early spring with the use of glyphosate, provided over-wintered downy brome is small, actively growing, and weather conditions are favorable for herbicide uptake and translocation.
Table 1. Control of downy brome before or after seeding but prior to crop emergence
Spring in-crop Application: In Canada, chemical control options in winter wheat and fall rye are limited. Fall application of Sencor is registered for downy brome is registered in winter wheat Apply after the winter wheat crop has started tillering (past the three leaf stage) and initiated secondary roots. Sencor is only registered for Norstar winter wheat. There are no herbicides registered to selectively control downy brome in fall rye.
|Credit; Cheminova Glyphosate; Factor; Glyfos; Renegade; Sharpshooter; Sharpshooter Plus; Touchdown iQ||0.51 – 0.77||3-6 inches (8-15 cm) tall||All crops can be seeded soon after the application |
|Maverick II; Vantage Plus||0.38 – 0.57|| || |
|Factor 540; Renegade 540; R/T 540; Roundup Transorb; Roundup Ultra 2; Roundup WeatherMax||0.33 – 0.51|| || |
|PrePass||PrePass A: 0.04 L||1 – 4 LS||Only barley, oats and wheat can be seeded soon after the application|
| ||PrePass B: 0.5 L|| || |
|Roundup Transorb or Roundup WeatherMax + Express SG||0.33 + 6 g||Less than 10 cm tall and actively growing||Only barley, oats and wheat can be seeded soon after the application|
|Touchdown iQ + Express SG||0.51 + 6 g|| || |