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Weed Wisdom Jan 2017


Japanese Brome

by Dr. Bob Blackshaw

Farming Smarter began a 3-year project in fall 2016 studying Japanese brome control in barley with Western Applied Research Corporation in Scott, Saskatchedwan.Japanese brome (Bromus japonicas) exists as a winter annual or summer annual grass weed in the Canadian prairies. Plants typically reach a height of 80 to 100 cm. Stems are bent at the base and nodes are swollen and brownish in colour. Leaf blades are flat, 0.25-0.5 cm wide, 15-20 cm long, and covered in soft hairs.

Japanese brome seeds on stalks
Japanese brome seeds on stalks

It is easy to confuse Japanese brome with downy brome (Bromus tectorum), but there are some distinguishing characteristics. Downy brome has more open, drooping panicles with 20-30 mm long spikelets having 12-17 mm straight awns. Japanese brome spikelets are shorter (10-20 mm) and have shorter (8-10 mm) curved awns. Downy brome seed is a grey to reddish colour at maturity while Japanese brome seed is tan coloured. Indeed, the entire downy brome plant is purplish-reddish at maturity while Japanese brome is more of a pale tan colour.

a patch of Japanese brome in a crop
A patch of Japanese brome in a crop



Seed heads have long branches and pedicels, usually droop to one side when mature, and each branch has 1-5 spikelets. Japanese brome seed has little dormancy and usually doesn’t persist in the soil beyond 2-3 years. Optimum germination occurs at soil temperatures of 5-20 C; resulting in peak emergence in September-October and April-May.


Japanese brome growing in a field
Japanese brome growing in a field

Japanese brome is less common in southern Alberta and tends to grow in wetter sites compared with downy brome. Japanese brome, especially overwintered populations, can compete strongly with crops for soil nutrients and water. Glyphosate applied in fall or spring is highly effective on emerged Japanese brome plants. However, as Japanese brome can resume growth in spring at soil temperatures as low as 2-3 C, spring-applied glyphosate may be too late to prevent all of its competitive effects. There are numerous herbicide options for in-crop control in oilseeds and pulses, but far fewer herbicides are available for Japanese brome in cereals. Check the Crop Protection Guide for the best herbicide options for your crop.