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Weed Wisdom May 2017

Persian darnel has a flattened appearance. photo by Doug Waylett

by Dr. Bob Blackshaw

Persian darnel (Lolium persicum) is a summer annual grass weed present in the southern Canadian prairies. You can distinguish it from other grass weeds such as downy brome and wild oat by its reddish stem base colour and its narrow, dark green leaves that are rough on the upper surface and smooth and shiny on the lower surface. Plants typically reach a height of 50-70 cm and seed heads have 1-2 cm long spikelets in two rows. The plant appears somewhat flat as though someone pressed it. 

Persian darnel seed.Photo from Ohio State University

Persian darnel has light-colored seeds that are smooth, hairless, 2-3 mm wide and 10-12 mm long. Seed looks similar to thin barley seed or seed of range grasses such as perennial ryegrass and intermediate wheatgrass. Optimum germination occurs at soil temperatures of 10-25 C; resulting in peak emergence occurring in late-April to early June. Seed has little dormancy and usually doesn’t persist in the soil more than three years. 

Persian darnel, despite its short stature, can be a vigorous competitor with crops. At high infestation densities, recorded yield reductions reached 57, 70, and 83%  in wheat, canola and sunflower, respectively. Glyphosate burndown applications will give excellent control of emerged Persian darnel plants in early spring. Most Group 1 herbicides and some Group 2 herbicides provide effective in-crop control in many of our prairie field crops. However, Group 1 resistant Persian darnel populations have been documented in both Saskatchewan and Alberta, so be watchful for this in your area and choose your herbicides accordingly.