Mustard Seed Weed

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Wild Mustard Wild mustard ( Brassica kaber ) is a weed widespread throughout the United States. It is mainly a summer annual in New York, with smaller populations emerging in the fall. Its seeds The Weed Science Program’s goal at MSU is to provide science-based research and extension information on integrated weed management in field crops. Wild mustard control can be a challenge because this is a tough weed that tends to grow and create dense patches that out-compete other plants. Wild mustard is a pain, but it is a bigger problem for farmers than for home gardeners. Learn how to control the weed in this article.

Wild Mustard

Wild mustard (Brassica kaber) is a weed widespread throughout the United States. It is mainly a summer annual in New York, with smaller populations emerging in the fall. Its seeds can persist in the soil for many years. This weed is common particularly in small grains and fall-seeded forage crops.

Wild mustard population

Photo by Scott Morris of Cornell University

Wild mustard is one of 3000+ species in the mustard family . Several mustards species are fall/spring weeds in New York . For help identifying weedy mustards either in the rosette or flowering phase, please visit our mustard identification page.

Identification

Seedlings: Cotyledons are kidney- or heart-shaped and 5mm (1/5”) long by 8mm (3/10”) wide. The cotyledon also has an indentation at the tip. Young leaves (1-2 cm long- up to 4/5”) are oblong, egg- to club-shaped, and alternate with wavy-toothed edges. There are stiff hairs on both leaves and stems.

Wild mustard seedlings

Photo by Olivia McCandless via Cornell University Weed ID site

Mature plant: Flowering stems of the mature plant are upright and branched at the top. The lower portions of the stem have stiff, bristly hairs. The taproot is thin and branched, with fibrous smaller roots.

Wild mustard plant

Photo by Joseph LaForest of the University of Georgia, via Bugwood.org.

Wild mustard plants

Photo by Joseph M DiTomaso of UC-Davis, via Bugwood.org.

Leaves: The egg- to oval-shaped leaves are alternate, with scattered stiff, bristly hairs on the upper leaf surface and sunken veins. Lower leaves of the mature plant have longer leaf-stalks (petioles), are prominently lobed, and are often broadest at the tip. U pper leaves are smaller, hairy, have few to no lobes but sometimes toothed edges, and have very short to absent petioles.

Wild mustard leaf

Photo by Bruce Ackley of the Ohio State University, via Bugwood.org.

Mature wild mustard leaves

Photo by Bruce Ackley via The Ohio State University, Bugwood.org

Flowers/Fruit: Flowers appear in clusters (racemes) at the ends of branches. They are approximately 1.5 cm (3/5”) wide, with 4 yellow petals 8-12 mm (up to 1/2”) long. Fruit capsules (siliques) are long and narrow, 2-5 cm (up to 2”) long by 2-3 mm (~1/10”) wide, with a square-sided conical beak approximately half as long as the pod (see photo to right). Seeds are round, smooth, and black or dark purple-brown.

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Wild mustard yellow flowers

Photo by Bruce Ackley via Ohio State University

Wild mustard fruits

Photo by Joseph M. DiTomaso via University of California- Davis, Bugwood.org

Management

Chemical control

Wild mustard populations have developed resistance to herbicides in Groups 2 (ALS inhibitors like Raptor and Python), 4 (, synthetic auxins like 2,4 D, dicamba) and 5 (photosystem II inhibitors like atrazine). These have been recorded in several countries, with the most types of resistance found in western Canada. In the US, Group 2 resistance has been found in North Dakota. If you have problems controlling wild mustard consider whether you may be seeing resistance, and whether you have used any equipment recently purchased from the north central states or Canada in that field.

New York specific guidance can be found in the Cornell Crop and Pest Management Guides , or click above for the chemical control of wild mustard from Cornell’s turfgrass and weed weed identification app.

Non-chemical control

Wild mustard establishes quickly and can be very competitive, especially in high nitrogen fields. Emergence peaks in early to mid-spring. Nitrogen causes rapid growth of wild mustard, so in an infested field it helps to avoid over-fertilizing or side-dress later in the season. Shading reduces growth and seed production, so planting competitive crops where in problem fields can reduce weed-crop competition and wild mustard populations the following year. For example, densely planted cereal grains can out-compete wild mustard, as the grains overtop and reduce light for the weed.

In fields where wild mustard is a problem, plant large seeded crops a little deeper than usual and cultivate aggressively before the crop emerges. Throwing soil into the crop row as early as the crop can handle the disruption can bury emerging weed seedlings. You can also consider rotating to a late season crop and cultivating during the spring fallow period to flush and reduce the wild mustard seed bank.

Although there are currently no commercial biological control agents, ground beetles (carabids) do consume Wild Mustard seeds that lie on the soil surface.

References

Uva R H, Neal J C, DiTomaso J M. 1997. Weeds of the Northeast. Book published by Cornell University, Ithaca NY. The go-to for weed ID in the Northeast; look for a new edition sometime in 2019.

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Cornell University’s Turfgrass and Landscape Weed ID app. Identification and control options for weeds common to turf, agriculture, and gardens in New York; uses a very simple decision tree to identify your weed.

Many organic management suggestions are from Dr. Charles Mohler of Cornell University. Look for an upcoming book from Dr. Mohler on ecological management of weeds, from Cornell University Press.

I Will Take Action herbicide resistance chart, accessed Sept 2 2020.

Warwick, S. I., Beckie, H. J., Thomas, A. G. and McDonald, T. 2000. The biology of Canadian weeds. Chapter 8: Sinapis arvensis L.
(updated). Can. J. Plant Sci. 80: 939–961.

Profile on Wild Mustard from the Weed Report from Weed Control in Natural Areas in the Western United States. Contains extensive descriptions of chemical and non-chemical control.

University of Michigan Integrated Pest Management wild mustard page. This resource has excellent photos of the cotyledons and bristly stem-hairs of wild mustard.

Weeds

Winter/summer annual. Emerges in late summer, early fall or spring. In Michigan, several populations of wild mustard act as a summer annual. Flowering peaks in June and July, but can continue until the first frost.

Emergence:
Emerges from soil depths of 1-inch or less.

Seed:

Production Range: Approximately 1,200 seeds per plant.

Dispersal Mechanisms: Seed pod dehiscence (splitting open).

Longevity: Low persistence – 50% of the seed bank is reduced in less than one year, and it takes seven years to reduce the seed bank 99%.

Dormancy: Initially dormant. Dormancy is broken by a combination of changes in temperature, light, and nitrate levels.

Competitiveness:

One of the more competitive weeds with small grains, soybean, and corn. Winter cereal yields were reduced 13 to 69%, when the biomass was comprised of 1 to 60% wild mustard. Soybean yields were reduced 46% with 4 plants per yard of row and corn yields were reduced 1.5- to 2-fold and 5- to 6-fold at low and high wild mustard densities, respectively.

Preferred Soil/Field Conditions:

Grows on a wide range of soils.

Management:

Biological

Predation/grazing: Ground beetles (carabids) eat wild mustard seed lying on the soil surface.

Decay: No information.

Mechanical

Tillage: Seedlings are readily killed by tillage.

Rotary Hoeing: Hoe before weeds exceed 1/4-inch in height, once established wild mustard is difficult to control.

Flaming: Effective on small wild mustard.

Cultural

Crop rotation: Corn-soybean rotations will deplete wild mustard populations more rapidly than continuous wheat.

Planting date: Later planting will reduce wild mustard populations.

Chemical

Application timing and effectiveness: Several herbicides are effective for controlling wild mustard. Control is greater when herbicides are applied to smaller wild mustard plants. Please refer to E-434, “MSU Weed Control Guide for Field Crops,” for herbicide recommendations.

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Additional Information

Wild mustard can serve as an alternate host of nematodes and many insect pests.

Wild Mustard Weeds – Tips For Wild Mustard Control In Gardens

Wild mustard control can be a challenge because this is a tough weed that tends to grow and create dense patches that out-compete other plants. Wild mustard is a pain, but it is a bigger problem for farmers than for home gardeners. You can use both physical and chemical strategies to manage or eliminate wild mustard in your yard or garden.

About Wild Mustard Weeds

Wild mustard (Sinapis arvensis) is an aggressive weed native to Europe and Asia, but one which was brought to North America and has now taken root. It is an annual that grows to about three to five feet (1 to 1.5 meters) and produces yellow flowers. You will often see these plants growing densely by the roadside and in abandoned areas. They are mostly problematic in cultivated fields, but wild mustard plants can take over your garden too.

Controlling Wild Mustard Plants

Because it’s so tough, getting rid of wild mustard can be a real project. If you do not want to use chemicals in your garden, the only way to eliminate this weed is to pull it out. The best time to pull mustard weeds is when they are young. This is because they will be easier to pull out, roots and all, but also because removing them before they produce seeds will help limit future growth.

If you have too many to pull, you can mow down wild mustard before seed production, during the bud to bloom stages. This will limit seed production.

Unfortunately, there are no other cultural or biological control methods for wild mustard. Burning does not help, nor does allowing animals to forage. The seeds of wild mustard can actually be toxic to livestock.

How to Kill Wild Mustard with Herbicides

Herbicides can also be effective in controlling wild mustard. There are several different types of herbicides that will work against wild mustard, but there are some that the weeds have grown resistant to and that will no longer work.

There are different varieties of wild mustard, so first determine which type you have and then ask your local nursery or university agricultural department to help you select the right chemical.

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