HPIPM:Crabgrass

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Lilianae
Order	Poales
Family	Poaceae

Scientific Name

Digitaria

Common Name

crabgrass

Crabgrass (Digitaria sanguinalis)

Compiled by Mark B. Major, Montana State University, Teton County Extension

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

http://128.104.239.6/uw_weeds/extension/articles/lgsmcrab.htm

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

http://www.uri.edu/ce/factsheets/sheets/crabgrass.html

Identification and Life Cycle

Crabgrass (Digitaria sanguinalis) is an annual in the grass family (Poaceae). Leaves are flat, measuring 0.75-6 inches long and up to 0.5 inches wide, with a prominent mid-rib and pubescent on both sides. Crabgrass have membranous ligules that are truncated and have a jagged appearance. The sheath (area where the leaf and stem join) is covered with straight, long hairs. The stem is rather stout, may exhibit a decumbent (reclining) growth pattern, and additional roots may form at the soil/node region. The inflorescence consists of a panicle of branches with spikelets arranged in two rows of a flattened rachis. Large crabgrass may grow up to 3 1/2 feet in height.

Habitats

The preference is full or partial sun, moist to slightly dry conditions, and a heavy clay-loam soil. Habitats include disturbed areas of prairies, weedy meadows, edges of degraded wetlands, areas along roads and railroads, lawns and gardens, vacant lots, fields, grassy paths, and highly disturbed areas.

Impacts

Crabgrass can present significant challenges to corn growers if not managed properly. Crabgrass is also a problem in other cultivated crops.

Biology and Ecology

Crabgrass reproduces by seeds. When the soil temperature reaches 55-60 degrees F, crabgrass begins to germinate. However, the soil temperature must be in this range for a minimum of one week. Seeds germinate best from early spring to late summer. Crabgrass continues to grow until midsummer when days become shorter, and vegetative growth slows as plants enter their reproductive stage. Purplish seed heads form until frost kills the plants. Plants that emerge early in the season and have a long period of vegetative growth are much larger and more competitive than plants that germinate late in the season. Crabgrass has a prolific tillering or branching habit. A single plant is capable of producing 150 to 700 tillers and 150,000 seeds. Crabgrass seeds are dormant for a short period of time after they shed from plants. Most growth occurs during the hot weather of summer because of its C4 metabolism.

Management Approaches

Crabgrass cannot be controlled in one growing season because of the large number of viable seeds that accumulate in the soil from years of infestation. Controlling seed production for several years will help reduce the viable seed supply.

Biological Control

There are no biological control agents available for crabgrass.

Mechanical and Cultural Control

Crabgrass plants are very adaptive to mowing height. Plants can produce seeds at mowing heights as low as 1/2-inch.

Chemical Control

There is been one reported case of crabgrass resistance to ACC ase inhibitors in Wisconsin. For more information about this case please see: http://www.weedscience.org/Summary/USpeciesCountry.asp?lstWeedID=77&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 crabgrass

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
Sethoxydim	Inhibition of acetyl CoA carboxylase (ACCase)
*Poast		1 - 1.5 pints	Apply when crabgrass is less than 8 inches high. Rate depends on state and location, see label for maps. Apply before crop canopy covers crab grass and at least 14 days prior to cutting for dry hay.
Corn
Pendimethalin	Microtubule assembly inhibition
*Prowl H2O		4 pints	May be applied in conventional, minimum, or no-till as a preemergence, or postemergence herbicide until field corn is 30 inches tall or in the V8 growth stage.
Dry beans, Succulent Peas, Lentils
Imazethapyr; quizalofop	Inhibition of acetyl CoA carboxylase (ACCase)
*Assure II		8 - 10 ounces	Apply when crabgrass has 2-6 inches of lateral growth. Do not apply within 60 days of harvest in peas and lentils or within 30 days of harvest in dry beans.
Grass Grown for Seed
Quinclorac	Growth regulator
*Paramount		5.3 ounces	See label for specific grass seed crops and instructions.
Small Grains
Glyphosate	Inhibition of EPSP synthase
*Roundup Ultra Dry		9.5 - 19 ounces	Apply when crabgrass has 3 – 12 inches of growth. Apply before, during or after planting of cereal crops. Applications must be made prior to emergence of the crop.

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=Digitaria%20sanguinalis