HPIPM:Mayweed chamomile

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Asteranae
Order	Asterales
Family	Asteraceae
Subfamily	Asteroideae
Tribe	Anthemideae
Subtribe	Anthemidinae
Genus	Anthemis

Scientific Name

Anthemis cotula

Scientific Name Synonyms

Maruta cotula

Common Name

stinking chamomile

Mayweed chamomile (Anthemis cotulaL.)

Compiled by Andrew Hulting, Oregon State University,and Marjolein Schat, Cornnel University, from the following sources:

http://plants.usda.gov/java/profile?symbol=ANCO2

http://www.unce.unr.edu/publications/files/nr/2004/FS0408.pdf

http://www.whitman.wsu.edu/weeds/Dogfennel.html

Identification and Life Cycle

Mayweed chamomile (Anthemis cotula) is an annual plant in the sunflower family (Asteraceae). Mayweed chamomile has small, oval-shaped seed leaves (cotyledons). They are thick and smooth and become maroon on the underside with age. They are rarely seen, though, because they dry up rapidly as the plant begins to grow. The first true leaves grow opposite of each other on the stem, and are pointed and deeply divided. Subsequent leaves grow alternately along the stems, sparsely produce short hairs, and are finely divided several times. They release a distinctly foul odor and grow about 0.75-2.5 inches long and 1 inch wide. The mature plant is 0.5-2 feet tall with erect, branching, hairless stems. The plant produces a tap root and an extensive, fibrous root system that grows near the soil surface. Flowers are borne at the ends of branches and on 1-4 inch long, unbranched stalks in the axils of the leaf from May through October. The many yellow disk flowers are surrounded by 12-20 white ray flowers in one head. The white ray flowers each have 3 distinct teeth at their tips. Flower heads are approximately 0.75-1 inch in diameter, and the bracts (involucres) at their bases are lightly hairy. Each flower head produces numerous (thousands per plant) single, smooth seeds (achenes). Each is about 0.06 inch long and inside a covering with 10 ribs that run lengthwise along the seed. Corn chamomile (Anthemis arvensis L.) may be confused with mayweed chamomile. They are nearly identical, but corn chamomile does not produce a foul odor when the leaves are crushed. Pineappleweed (Chamomilla suaveolens (Pursh) Rydb.) is also a similar species, but the flower does not have ray flowers, and the leaves of mayweed chamomile are more finely divided. The leaves of pineappleweed tend to clasp the stem and they give off a pineapple scent when crushed.

Habitats

Infestations are often limited to low, wet areas, but mayweed chamomile is can be found in other areas. It adapts to various growing conditions, but prefers heavily disturbed, rich, gravelly soil. It is commonly found in waste areas, barnyards, cultivated fields, roadsides, alfalfa fields, meadows, overgrazed pastures, dry tailwater ponds, and along ditches, particularly if moisture is available or regularly applied through irrigation.

Impacts

Contact with mayweed chamomile can cause skin rashes to workers. Livestock that graze mayweed chamomile van develop blistered noses and mouths, and irritated mucous membranes. It also imparts a strong off-flavor to the milk of dairy animals if they graze it or eat it in hay. Mayweed chamomile is competitive, allelopathic (slows or stops growth of other plants), requires control in cropping systems, and may contaminate seed crops, requiring costly seed cleaning. It is a particular problem in cereal crops and grasses grown for seed.

Biology and Ecology

Mayweed chamomile reproduces only by seed. Seeds germinate throughout the growing season. Seeds can remain viable in the seed bank for more than 10 years. Flowering occurs from May through October but peak flowering occurs in June and July.

Management Approaches

It is most important to prevent the production and spread of mayweed chamomile seed.

Biological Control

There are currently no biological control methods available for mayweed chamomile.

Mechanical and Cultural Control

Isolated mayweed chamomile plants and small infestations can be removed by hand pulling and digging before viable seed is produced. Cultivation is most successful if done when the plant is in the seedling stage, before an extensive root system develops and before the plant flowers and produces seeds. Repeated cultivation may be necessary to control this weed. Mowing or flailing mayweed chamomile is not very effective. However, some success may be achieved if performed immediately before the plant flowers. If mowed too early, the plant grows more prostrate and can produce flowers below the height of a mower blade set to minimize damage to other desirable plants. A second mowing may be required to remove flowers when the season is long, moisture is available and the plants regrow and flower after the first mowing. Mayweed chamomile is not an exceptionally strong competitor, so maintaining a vigorous pasture with proper irrigation, fertilizer application, and harvesting can limit spread in forage production systems. Avoid overgrazing and excessive cultivation.

Chemical Control

A number of chemical control options are available for mayweed chamomile. In 1997 there were reports of ALS inhibitor resistant mayweed chamomile at several sites in Idaho. For more information on these reports refer to the following website: http://www.weedscience.org/Summary/USpeciesCountry.asp?lstWeedID=19&FmSpecies=Go Herbicide resistance in this species is now widespread across much of the Pacific Northwest.

In the table below are examples of herbicides that can be used to manage mayweed chamomile

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

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.

References

For more images please visit IPM Images: http://www.forestryimages.org/browse/subthumb.cfm?sub=5106&Start=1&display=16&sort=2