Pest Profile: Shepherd’s Purse
Shepherd’s purse typically appears in the early spring. It begins flowering early and can produce seeds throughout the season if left unchecked. Because each plant can produce up to 45,000 seeds, early control of the weed is critical. Fall herbicide applications are most effective, as shepherd’s purse is difficult to control in the spring.
Shepherd’s purse resembles its cousins in the Mustard family but can be distinguished by its orange-yellow to reddish heart-shaped seed pods that attach to the stalk at the pointed end. Its stems are branched and can grow 10-60 cm high, with leaves that alternate about 1 per lobe. Leaf blades are variable and oblong in shape, shallowly to deeply and coarsely toothed, and about 5-10 cm long. Flowers bloom from early spring to late fall. They resemble wild mustard, but can be distinguished by their white colour and smaller size (about 3-8 mm across), and gather in rounded clusters at the ends of stems and branches.
- Winter annuals like shepherd’s purse can be hard to control in the spring if they germinate in the fall or late summer. Treat with cultivation or a herbicide application in the fall prior to snowfall for best results.
- Shallow, vertical tillage can help control shepherd’s purse.
- Group 2-resistant weeds have been found in Alberta and Saskatchewan, but as of yet has not been found in Eastern Canada.
- If attempting to control in the spring, treat early with full rates of a registered broadleaf herbicide. Bromoxynil with MCPA and clopyralid with MCPA are two effective combinations.
- Glyphosate can be effective in post-harvest and pre-seed applications.
REFERENCES AND ADDITIONAL READING
“Ontario Weeds: Shepherd’s Purse.” Ontario Ministry of Agriculture, Food and Rural Affairs. Online. https://bit.ly/2JrZiIn
“Shepherd’s-Purse, Capsella bursa-pastoris.” WeedInfo.CA. Online. https://bit.ly/2yFTEy7
“Shepherd’s Purse.” Manitoba Agriculture. Online. https://bit.ly/2yHyzDb
Raine, Michael. “Weed of the Week: Shepherd’s Purse.” Western Producer. 21 May 2015. Online. https://bit.ly/2qqX6rX