Photographer: USDA APHIS Archives Affiliation: USDA APHIS Archives Source: Bugwood.org Copyright: CC BY 3.0 US
The erect, profusely tillering annual grass R. cochinchinensis is characterized by pale, green-colored foliage, brace roots near the base of the plant with a cylindrical spikelet seedheads. Also it is known for, siliceous hairs on the leaf sheath that can penetrate and irritate the skin. Itchgrass grows up to a height of 4 m or more. The inflorescence is a cylindrical raceme that is 3 - 15 cm long. The floral units consist of a sessile spikelet, pedicellate spikelet and internode. The pedicel is fused to the swollen floral internode. The spikelets are awnless, 3.5 - 6 mm long, and 2.5 - 3 mm wide. The floral units separate and fall as soon as they mature, from the top of the raceme downwards.
Itchgrass is rated among the worst weeds in the world and is considered a serious problem in soybean (Glycine max (L.) Merr.), corn, cotton (Gossypium hirsutum L.), peanut (Arachis hypogaea L.), upland rice (Oryza sativa L.), and other crops in tropical regions of the world. In Louisiana, R. cochinchinensis, referred to as raoulgrass, is a major weed problem in sugarcane (Saccharum spp.), soybean, and corn.
Seeds can be spread from infested areas to non-infested areas by many things including, birds, flood water, rodents, and farm machinery. The spread of R. cochinchinensis in Louisiana has been attributed in part to movement of equipment and road matting materials used during the extensive oil exploration that occurred in the late 1970s and early 1980s. By 1980, the weed infested 38 Louisiana parishes on about 80,940 hectares.
It is speculated that itchgrass was introduced to the United States in plant material or on equipment imported from the West Indies.
Native Origin: Africa, Asia, and Australia
U.S. Habitat: Rottboellia cochinchinensis is a weed of warm-season crops preferably in tropical and subtropical climates. It also grows along roadsides and in other open, well-drained sites and is an important species in old field succession but it can be found in wet places, and even in shallow water. Itchgrass is most troublesome between 800 and 1300 m in elevation. Rainfall is a main limiting factor below 1300 meters, while above this elevation, temperature is the main limiting factor.
U.S. Present: AR, FL, GA, IL, IN, LA, MO, MS, OK, NC, PR, TX
For a partial county distribution map provided by EDDMapS click here
Invasive Johnsongrass (Sorghum halepense)
Shallow tillage promotes itchgrass germination prior to planting. Emerging seedlings could then be controlled by additional mechanical means or with herbicides. Failure to control itchgrass seedlings after soil preparation, may result in extremely high densities that will significantly reduce crop yields.
For more information on the progress research is making on itchgrass management click here
USE PESTICIDES WISELY: Always read the entire pesticide label carefully, follow all mixing and application instructions and wear all recommended personal protective gear and clothing.
Contributions from Texas Invasives for this species page are greatly appreciated.
Aison, S., M. K. Johnson, and T. R. Harger. 1984. Role of birds in dispersal of itchgrass (Rottboellia exaltata (L.) L. f.) seeds in the southeastern U.S.A. Proc. Ecol 6:307–313.
Alves, P. L. 2003. Identification and characterization of different accessions of itchgrass (Rottboellia cochinchinensis). Weed Science 51: 177-180.
Bowen, B., K. Johnson, S. Franklin, G. Call, and M. Webber. 2002. Invasive Exotic Pest Plants in Tennesee. Journal of the Tennessee Academy of Science 77(2): 45-48.
Freshwater, I. T., A. J. Benson, and T. F. Hall. 1986. Itchgrass Rottboellia cochinchinensis—Burdekin infestation and legislative control program. Proc. Aust. Soc. Sugar Cane Technol. 155–160.
Holm, L. G., D. L. Plucknett, J. V. Pancho, and J. P. Herberger. 1977. The World’s Worst Weeds, Distribution, and Biology. Honolulu, HI: University Press of Hawaii. 609 p.
Millhollon, R. W. 1980. Itchgrass—a weed of world-wide concern. Sugar J 43:16.
NAPPO (North American Plant Protection Organization). 2003. Pest Fact Sheet: Rottboellia cochinchinensis (Lour.) Clayton. NAPPO-PRA / Grains Panel Pest Fact Sheet.
Strahan, R. E., J. L. Griffin, D. B. Reynolds, and D. K. Miller. 2009a. Interference between Rottboellia cochinchinesis and Zea mays. Weed Science 48:205-211
Strahan, R. E., Griffin, J. L., Jordan, D. L., & Miller, D. K. 2009b. Influence of Adjuvants on Itchgrass (Rottboellia cochinchinensis) Control in Corn (Zea mays) with Nicosulfuron and Primisulfuron1.