Pest Information
Common Name: Flixweed
Family Name: Descurainia sophia
Latin Name: Cruciferae (Mustard Family)
Provincial Designation: Common
Life Cycle: Annual, Winter Annual, Biennial
Mode of Spread: Seed

Detailed Information
Provincial Situation: Flixweed occurs in scattered localities throughout Alberta, usually in grain fields, gardens, fence lines, waste places, and along roadsides. According to Alberta Weed Survey (2003), the frequency, density and ranking of flixweed in various agricultural ecoregions is as follows:

Agricultural EcoregionFrequency1(%)Density2 (%)Ranking
Mixed Grassland7.81.413
Moist Mixed Grassland10.52.810
Fescue Grassland13.24.811
Aspen Parkland2.41.432
Boreal Transition---
Peace Lowland---
Alberta (All regions)3.82.529

1Frequency: Percent of fields in which flixweed occurred
2 Density = Average number of flixweed in occurrence fields.

Description: Grayish-green annual or winter annual, which grows up to 1 m high. The leaves are alternate, divided 2 – 3 times into narrow segments. Flowers are small in dense cluster at the ends of branches. The pods are slender, 1.6 cm long. The flowers are small, with four pale yellow petals and are clustered at the top of the stem and the ends of branches. As the seeds mature the main flower stalks elongates so the inflorescence makes up to the ½ of the total height of the plant. The seeds are orange in color and form a single row on each side of the seedpod.
Growth and Development (Life Cycle): Emergence:Seedling emerges mainly in the fall and the early spring.
Seed Production: Flixweed produces an average of 75-650 seeds per plant. A large plant may produce upwards of 700,000 seeds.
Seed germination: Seeds germinate most readily in the fall. Some seeds also germinate in the spring.
Dormancy: Seeds do not undergo a dormant period before they germinate.
Longevity in the soil: Seeds can remain viable for up to 3 yrs.
Dispersal: Most seed falls near the parent plant. Wind, water, machinery, and animals transport flixweed seed.
Reproduction (Dispersal): By seeds only, however, plants can re-sprout when rootstalks are fragmented during tillage operation.
Economic Importance (Beneficial Aspects):

Detrimental:  Flixweed is toxic to livestock, causing blindness, staggering, and loss of ability to swallow. All parts of the plant contain poisonous levels of nitrate. The seeds contain poisonous isoallyl thiocyanates and irritant oils. Large quantities of the plant must be consumed for long periods of time for poisoning to occur. Over-winter rosettes are strong competitors because they grow rapidly in the spring and use valuable spring moisture before fields can be seeded. Spring-emerging flixweed seedlings do not compete as well, especially in heavy crop stands. Flixweed can be a severe problem in perennial forage crops grown for seed.

Origin: Flixweed is native to Europe and northern Africa. It probably arrived in North America in the mid-1800s as an impurity in crop seed, and was widespread by the 1920s.
Flowering: Flowering timing: Over-winter rosettes begin to flower near the end of the may. Flixweed that germinate in the spring starts to flower in mid June. Both growth forms continue to flower through the summer
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 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 flixweed as compared to spring applications.
Spring Pre-seeding Weed Burndown Application: In direct seeding system, flixweed can be controlled in the early spring with the use of burndown herbicides, such as glyphosate provided weeds are small, actively growing, fall rosettes have not bolted, and weather conditions are favorable for glyphosate 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 winter weeds. 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 flixweed control in cereals, oil-seed and pulse crops. These herbicides will only provide good control if the weeds are in the seedling stage. By in-crop treatment time, most of the flixweed rosettes have already bolted and will not be controlled. (See Herbicide Selector for details)

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Last Modified: January 19, 2009

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