||Stinkweed is found in all parts of the province. The frequency, density and the ranking of stinkweed in various ecoregions of Alberta is listed in Table 1. Table 1. Distribution of stinkweed in Alberta
|Agricultural Ecoregion||Frequency1 (%)||Density2 (%)||Ranking|
|Moist Mixed Grassland||19.3||44||6|
|Fescue Grassland ||32.5||1.4||6|
|Aspen Parkland ||18.8||4.3||7|
|Boreal Transition ||22||5.1||10|
|Peace Lowland ||48.3||10.3||3|
|Alberta (All regions)||20.1||5.5||7|
1 Frequency: Percent of fields in which flixweed occurred
2Density = Average number of flixweed in occurrence fields.
Source: Leeson et al (2005). Prairie weed surveys. Cereal, oilseed and pulse crops 1970s to 2000s.
||Annual or winter annual, growing to 0.6 m. The stems are smooth, erect, and often branched. The lower leaves can be in the form of a rosette. In erect plants, the leaves are alternate and without hairs. The upper leaves clasp the stem. The flowers are small, stalked, and have white petals. The seed pods are rounded and surrounded by a broad winged border, become yellow to greenish-orange at maturity.
|Growth and Development (Life Cycle):
||Emergence: The emergence of summer annuals occurs mainly in the early spring. The seeds of winter annuals germinate in late summer. The seedlings overwinter and continue to grow in the spring.Seed Production: Stinkweed can produce up to 15,000 seeds per plant.
Seed germination: While seed germinates in greatest number early in the spring, from mid April to mid May, there is a second flush of emergence in the fall. Some germination may also occur sporadically throughout the summer, particularily when soil has been cultivated and when rain has provided an adequate moisture supply. Seed requires both light and temperature for germination.
Dormancy:Seeds can remain dormant for long periods but under conditions of adequate light and moisture and alternating soil temperature, freshly harvested seeds germinate. Germination is sensitive to dry conditions. Seed dormancy can be broken by cold temperatures. In the fields, nitrate application will stimulate germination.In a conventional and high disturbance seeding systems, soil disturbance increases the level of germination due to the exposure of seeds to light. Most of the seedling emerge from the upper 50 mm of soil with most coming from the top 30mm.
Longevity in the soil: The seeds can live for up to 6 years in the tillage zone. Seeds that are buried deeper than the tillage zone can live for up to 20 years and germinate when they come close to the surface. Seed dormancy is enhanced by a thick seed coat.
Dispersal: Seeds are dispersed by wind and water. Seeds will float in water for 24 hrs and their dispersal is possible under irrigation. Animals also plays a big part in the spread of this weed. Viable seeds have been found in bird dropping and cow manure.
|Where it Grows (Habitat & Ecology):
||It grows anywhere on disturbed soil, including cultivated soil. In western Canada it is a serious weed in oilseed crops
|How it Spreads (Mode of Spread):
||Mainly by seeds
||Mainly by seed
|Economic Importance (Beneficial Aspects):
Detrimental: Stinkweed compete with crops for moisture and nutrients. Overwintering stinkweed grows quickly in the spring and can deplete moisture quickly, especially in drier areas. Stinkweed densities as high as 750 plants per metre square can reduce wheat yields by 20%. Young plants when eaten by livestock, can produce an off flavour in both the meat and milk.
Beneficial: Not known
Flowering timing: Seedlings that emerge in the spring (summer annual) flower within 30-50 days, Seedling that emerge in the fall (winter annual) flower in the early spring Flower and seed production of both forms take place throughout the summer.
Flower Color: White
|How to Control:
||Control of fall rosettes is important so that seed is not formed early in the following spring. In conventional tillage systems, plants with developed pods should not be turned under because they can continue to ripen on the stalks in warm soil.
Tillage:Tillage is not an effective way to control these weeds. Moreover, tillage contributes to soil erosion and deplete seedbed moisture.
Crop Rotation: Crop rotation alone will not control stinkweed. A summerfallow year in the rotation will help reduce the seed levels in the soil. Seedling will still germinate from existing seeds.
||Control of stinkweed 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 flixweed; however, this treatment will not control spring emerging seedlings. In the fall, flixweed 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. A study conducted at Scott, SK, showed that fall applications of 2,4-D provided excellent control of stinkweed and flixweed as compared to spring applications
Spring Pre-seeding Weed Burndown Application In direct seeding system, stinkweed can be controlled in the early spring with the use of glyphosate herbicide, 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, CLEARFIELD and Liberty Link provides another option for the control of stinkwed. 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 stinkweed control in cereals, oil-seed and pulse crops (For details on these herbicide treatments, see Roping the Web's The Herbicide Selector Tool). These herbicides will only provide good control if the stinkweed is in the seedling stage (spring germinated stinkweed) . By in-crop treatment time, most of the stinkweed rosettes have already bolted and will not be controlled.