HPIPM:Flixweed

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Rosanae
Order	Brassicales
Family	Brassicaceae
Genus	Descurainia

Scientific Name

Descurainia sophia

Common Name

flixweed

Flixweed (Descurainia sophia)

Compiled by Terry Angvick, Montana State University, Sheridan County Extension

and Marjolein Schat, Montana State University from the following sources:

http://plants.usda.gov/java/profile?symbol=DESO2

http://www.illinoiswildflowers.info/weeds/plants/flixweed.htm

Howard, Janet L. 2003. Descurainia sophia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/plants/forb/dessop/all.html [2008, October].

Identification and Life Cycle

Flixweed (Descurainia Sophia) is in the mustard family (Brassicaceae). Other common names for flixweed include herb Sophia and pinnate tansymustard. This adventive biennial or annual plant is 1/2–2½ feet tall. It branches occasionally, and is more or less erect. The stems are greyish or bluish green and pubescent; sometimes the lower stem is nearly glabrous and light purplish green. During the 1st year, biennial plants consist of a low-growing rosette of basal leaves spanning up to 1 foot across. The cauline leaves of annual and 2nd-year biennial plants alternate along the flowering stems, spanning up to 8 inches long and 4 inches across and becoming progressively smaller higher up on the stems. Both the basal and cauline leaves are double or triple pinnately lobed, greyish or bluish green, and finely pubescent. The basal and lower cauline leaves have long petioles, while the petioles of the upper cauline leaves are shorter. The upper stems terminate in racemes of flowers about 2-12 inches in length. The flowers bloom near the apex of each raceme, while the siliques (slender seedpods) develop below. Each small flower is about 1/8 inch across, consisting 4 pale yellow petals, 4 green sepals, 6 stamens with yellow anthers, and a pistil with a single style. Both the sepals and petals are quite narrow (especially the latter); the petals are about the same length as the sepals or a little shorter. There is no noticeable floral scent. Each flower is replaced by a silique about 1 inch in length. This silique is narrowly cylindrical and contains 10-20 tiny seeds in a single row. The slender pedicels of the siliques (or flowers) are about 1/2 inch in length. The siliques and their pedicels are spreading-ascending in relation to the stalk of the raceme. Each tiny seed is somewhat flattened and oblongoid; it is some shade of orange-brown. The root system consists of a stout taproot.

Habitats

Flixweed occurs in waste areas, fields, roadsides, and ditchbanks. It also grows in pastures, cultivated areas, along roadsides, and in waste areas.

Impacts

It is becoming an increasing problem in alfalfa fields. In agricultural fields, flixweed is competitive for moisture and nutrients, reducing overall crop yields. All parts of the plant are poisonous, causing blindness, staggering, and loss of ability to swallow.

Biology and Ecology

Flixweed reproduces solely from seed. Germination usually begins in winter or early spring, depending upon latitude and elevation and flixweed is one of the first plants to appear in spring. The blooming period occurs from late spring to mid-summer and lasts about 2 months. Fruits ripen in summer or early fall, and plants begin to dry out and die at that time. Fruits burst and disperse seed as the plant dries. Flixweed produces an average of 75-650 seeds per plant. A large plant may produce upwards of 700,000 seeds. Wind, water, machinery, and animals transport flixweed seed, although most seed falls near the parent plant. Fall-germinating seeds overwinter as rosettes.

Management Approaches

Effective control can be achieved with mechanical and herbicide treatments. Seedlings are sensitive to most herbicides, even at low dosages.

Biological Control

There are no biological control organisms reported for flixweed.

Mechanical and Cultural Control

Canopy closure, litter accumulation and/or growth interference from later-successional species tend to exclude flixweed over time. Since flixweed is an early seral species, minimizing soil disturbance and seed dispersal and maintaining a healthy plant community is the best way to prevent establishment of flixweed.

Chemical Control

Although there have been no reports of herbicide resistant populations of flixweed in the United States, there has been resistance to ALS inhibitors reported in China. For more information on the report of resistance, please see http://www.weedscience.org/Summary/USpeciesCountry.asp?lstWeedID=237&FmSpecies=Go

For herbicide recommendations for specific grain rotations and weeds in Montana, please see the MSU Herbicide Chooser Tool.

Examples of herbicides that can be used to manage flixweed

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Herbicide Active Ingredient trade name	Mode of Action	Product per Acre	Application Time or Growth Stage
Alfalfa
Imazamox	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Raptor		4 - 6 ounces	Apply when seedling alfalfa is in the second (2nd) trifoliate stage or larger and when the majority of the weeds are 1-3 inches tall. Can be applied to established alfalfa in the fall, winter, or in the spring to dormant or semi-dormant alfalfa, or between cuttings. Any application should be made before significant alfalfa growth or regrowth (3 inches)
Pasture, Rangeland, and Grass for Hay or Silage
2,4-D; dicamba	Action like indole acetic acid (synthetic auxins)
*Weedmaster		1 pint	Apply when flixweed is less than 3 inches tall. Best results will be obtained if applied at the germinating stage of weeds. Under favorable conditions, this is usually 7-10 days after planting these grasses.
Wheat (except Durum and Wampum varieties of Spring Wheat) and Barley
Thifensulfuron; tribenuron; metsulfuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Ally Extra		0.3 - 0.4 ounce	Apply in tank mixtures with 2,4-D or MCPA postemergence, but before bloom (refer to Tank Mixtures section of label for additional details). Make applications after the crop is in the 2-leaf stage, but before the flag leaf is visible.
Durum and Wampum varieties of Spring Wheat
Thifensulfuron; tribenuron; metsulfuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Ally Extra		0.3 - 0.4 ounce	Apply in tank mixtures with 2,4-D or MCPA postemergence, but before bloom (refer to Tank Mixtures section of label for additional details). Make applications after the crop is tillering but before boot. Applications to durum and wampum varieties should be made in combination with 2,4-D.
Wheat, Barley, Winter Oat, and Triticale
Thifensulfuron; tribenuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Harmony Extra		0.45 – 0.9 ounce	Apply after crop is in the two leaf stage, but before the flag leaf is visible.
Wheat, Barley, and Triticale
Tribenuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Express		0.5 ounce	Apply after crop is in the two leaf stage, but before the flag leaf is visible. Do not harvest within 45 days of last application. Apply flixweed is past the cotyledon stage, actively growing, and less than 4 inches tall.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=flixweed&Start=1&results=20