Weed of the Week: shepherd’s purse

Capsella bursa-pastoris was limited to wetter areas and field edges when tillage was common.

However, reduced tillage created new opportunities for the winter annual weed, which is more commonly known as shepherd’s purse.

Along with narrow-leaved hawk’s beard, cleavers, flixweed and stinkweed, this member of the mustard family appears early in spring to rob fields of water and nutrients.

Fall herbicide programs can help control it, but like stinkweed, it can be tough to control in spring. The recent trend to shallow, vertical tillage has provided some control.

The weed is also known as shepherd’s pouch, St. James weed, pepper plant, mother’s heart, poor man’s parmacettie, sanguinary, shepherd’s heart and capsella.

It has joined the ranks of weeds that have developed resistance to Group 2 herbicides in Saskatchewan and Alberta.

Cotyledons are oval and have rounded tips when it is a seedling. The first leaves are lobed, and the leaves are covered in star-shaped hairs.

The immature plant’s leaf margins are highly variable, making identification tricky. They can be shallowly lobed or deeply cut.

The stems are sparsely branched and covered with star-shaped hairs. The stem leaves alternate. Balsal lobes of the leaves are pointed and clasp at the stem.

The weed grows up to 90 centimetres when not controlled and sprouts from a rosette at the ground. Mature plants have white flowers with four petals.

Flat pods form with a notched top and a small beak and each contains about 20 seeds.

Plants produce 45,000 seeds each. It begins flowering early and continue to produce seed throughout the season if allowed to reach maturity.

Seeds are orange, oblong and have a pitted surface.

Broadleaf herbicides are available that can control it in spring crops, but it needs full rates and early treatment to fully stop the pest. Bromoxynil with MCPA and clopyralid with MCPA can be effective.

Both work in cereals and flax and there is a minor use expansion of Curtail (clopyralid) for canaryseed. As well, Buctril (Mextrol, Badge and Logic) is also registered for canaryseed.

The weed can run amok in non-herbicide tolerant broadleaf crops.

In-crop applications of Odyssey and imazethapyr are effective in peas.

Glyphosate is effective in post harvest and pre-seeding applications.

The weed is found in most areas of the Prairies with the highest populations in the canola belt.

However, fewer instances of shepherd’s purse are seen in the brown soil zone and Manitoba’s southern Interlake and Red River valley regions.

Some herbal remedies are created using the weed and its seed, but it contains glucosinolates, which can be hard on the digestive tract.

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