| Provincial Situation: |
Shepherd’s purse is widely distributed in Alberta. The frequency, density and ranking of this species in various eco-regions of Alberta(Table 1).
Table 1. Distribution of Shepherd’s purse in Alberta | Agricultural Ecoregion | Frequency1(%) | Density2 (%) | Ranking | | Mixed Grassland | 13.3 | 4.5 | 20 | | Moist Mixed Grassland | 2.7 | 3.2 | 21 | | Fescue Grassland | 15.9 | 5.3 | 7 | | Aspen Parkland | 14.8 | 3.4 | 13 | | Boreal Transition | 16.9 | 2.8 | 17 | | Peace Lowland | 13.3 | 4.5 | 20 | | Alberta (All regions) | 12.1 | 1.6 | 20 |
1 Frequency: Percent of fields in which shepherds purse occurred
2Density = Average number of Shepherd's purse in occurrence fields.
Source: Leeson et al (2005). Prairie weed surveys. Cereal, oilseed and pulse crops 1970s to 2000s. |
| Description: |
Shepherd’s purse is an erect growing winter annual. Its stems are either solitary or branching at the base, 2.5 cm to 50 cm high; basal leaves form rosettes on ground, are often deeply lobed. Stem leaves are much smaller and stalkless; flowers are small, white and inconspicuous. Seeds are borne in a triangular or heart-shaped pods with the stalk on the pointed side |
| Growth and Development (Life Cycle): |
Emergence: Seedling emerges mainly in the fall and the early spring.
Seed Production: There are 10-12 seeds per capsule. A single Shepherd's-purse plant is capable of producing up to 38,500 seeds.
Seed germination: Shepherd's purse is a winter annual, germinating in both fall and spring if seeds receive light. Some seeds of shepherd’s purse are capable of germinating throughout the growing season.
Dormancy: Freshly harvested seed is dormant and requires a period of stratification followed by exposure to light in order to germinate. The presence of nitrate can to some extent overcome the need for stratification. Burial of seeds in soil under natural conditions allows after-ripening to take place. Once a sufficient period has elapsed, seeds germinate readily on exposure to light.
Longevity in the soil: Seeds can remain viable in the soil for many years.
Dispersal:Seeds are dispersed around the parent plant as the pods split open. Seeds are small enough to be dispersed over long distances by wind water, and animals. |
| Reproduction (Dispersal): |
Reproducing mainly by seeds,however, fragmented plants have to ability to transplant themselves |
| Economic Importance (Beneficial Aspects): |
Detrimental: Shepherd’s purse commonly harbors fungi, which are transmitted to cabbage, turnips and other members of mustard family.
Beneficial: Not known |
| Origin: |
A European plant introduced into North America in the 1700s. |
| Flowering: |
Flowering timing: Flowering from early spring to late fall |
| How to Control: |
Cultural Controls
Cultivation:Tillage soon after seed germinate will kill the seedling. However, tillage is not an effective way to control this weed because plant can re-sprout when rootstocks are fragmented during tillage operations. Moreover, intensive tillage is not compatible with modern farming practices as it contributes to soil erosion.
High Seeding Rates: Any crop seeded at high seeding rate will compete successfully with shepherd’s purse |
| Chemical Control: |
Control of fall rosettes is important in the fall. Over-winter rosettes are strong competitors because they grow rapidly in the spring and take a great deal of moisture before spring seeding. Those, which escape tillage or weed burn-down treatment, are usually too mature for control with herbicides in the crop.
Late Fall Application Late fall applications of 2,4-D or MCPA provide the most economical and consistent control of emerged winter rosettes of shepherd’s purse; however, this treatment will not control spring emerging seedlings. In the fall, shepherd’s purse is small, actively growing, and are susceptible to herbicide application. Moreover, the environmental conditions in the fall are more favorable for herbicide translocation than in the early spring.
Spring Pre-seeding Weed Burndown Application In direct seeding system, shepherd’s-purse can be controlled in the early spring with the use of burndown herbicides, provided weeds are small, actively growing, fall rosettes have not bolted, and weather conditions are favorable for herbicide uptake and translocation
Herbicide resistant crops: The use of herbicide resistant crops such as Roundup Ready canola and CLEARFIELD canola and wheat provides another option for the control of shepherd’s purse. For best results, applications should be made early, when weeds are small and before the rosettes have bolted
Spring in-crop Application A number of herbicides are registered for shepherd’s purse control in cereals, oil-seed and pulse crops (For details see Herbicide Selector Tool). These herbicides will only provide good control if the Shepherd’s purse is in the seedling stage (spring germinated Shepherd’s purse). By in-crop treatment time, most of the Shepherd’s purse rosettes have already bolted and will not be controlled. |
