Photograph of a close up of itchgrass inflorescences. The itchgrass is growing in a field in Thailand.

Itchgrass quick facts

Page snapshot: Quick facts about itchgrass (Rottboellia cochinchinensis), a major agricultural weed.


Topics covered on this page: What is itchgrass?; How is itchgrass identified? Where did itchgrass come from?; How does itchgrass spread?; What are the impacts of itchgrass?; How can itchgrass be controlled?; Resources.

Credits: Funded by the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Page by Naomi Schulberg (2023)

Updates: Page last updated August 14, 2023.

Image above: Itchgrass (Rottboellia cochinchinensis) inflorescences, Nakhon Nayok Province, Thailand, in the native range of itchgrass, 2009. Photo by Tony Rodd (flickr, Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license).

What is itchgrass?

Itchgrass or raoulgrass (Rottboellia cochinchinensis) is an annual C4 grass that is considered to be one of the worst weeds in the world. It is especially harmful in agricultural settings.

Itchgrass germinates in the summer and it is most commonly found in tropical or subtropical climates; while best suited to sunny conditions, is relatively tolerant of shade and a wide variety of environmental conditions. It is also often found in sites prone to disturbance, as it easily outperforms native grasses when establishing after a disturbance.


Photograph of a thick clump of itchgrass growing in Lake Charles, Louisiana. The photo shows tall, green grass in the foreground, with other vegetation in the background.

Itchgrass growing in Lake Charles, Louisiana, U.S.A. Photo by Irvin Louque (iNaturalist photo 21270229, Creative Commons Attribution 4.0 International license, image cropped and resized).

How is itchgrass identified?

Itchgrass can grow to be up to 10 feet (about 3 meters) tall and forms clumps. Its leaves have broad white midribs and are rough to the touch. The leaf sheath has small hairs that can penetrate skin, giving itchgrass its name. Its flowers are arranged in a racemose inflorescence that is around 4 inches (10 centimeters) long.


A compilation of four photographs of itchgrass. The top left image is of a full above-ground clump of grass. The top right image is of a singular inflorescence. The bottom left image is of a seedling. The bottom right image is of three seed dispersal units (seed-containing structures).

Where did itchgrass come from?

Itchgrass is native to tropical Africa and Asia to northern Australia. Today, it is present in the U.S., the Caribbean, and Central and South America.

Itchgrass may have been brought to from the Philippines to southern Florida in the early 1900s as a forage grass. It is currently listed as a noxious weed in 12 states in the Southeast and the Midwest, but the full extent of its spread is unclear.


Photograph of itchgrass growing on the left side of a dirt road in Madagascar.  The itchgrass is growing in a thick clump with stems arching toward the road.

Itchgrass growing along a roadside in northern Madagascar, 2015. Madagascar is considered to be in the native range of itchgrass. Photo by Bat (flickr, public domain).


A map of the United States and Canada with several states (mostly in the Southeast) colored green. The rest of the states are not colored in.

Map of the distribution of itchgrass in the United States and Canada. States with reports of itchgrass are shown in green. Map from EDDMapS. 2023. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/; last accessed August 3, 2023.

How does itchgrass spread?

Itchgrass seed spreads by seed. The grass is adapted for ant dispersal, and the dispersal units (seed-containing structures) have elaisomes on them. Elaisomes are attractive to ants because they contain proteins and fats. In addition to ants, mature itchgrass seeds can be spread by other animals (livestock, birds), water, and farm equipment. Itchgrass seed can also spread as a contaminant in seeds of agricultural crops.

Itchgrass produces seeds prolifically; one itchgrass plant may produce more than 16,000 seeds. Plants can start producing seeds in as few as six weeks after they appear above the soil surface. 


Photograph of itchgrass growing in a field in Thailand. The photo shows a close-up of the inflorescences, which are cylindrical.

Itchgrass, Nakhon Nayok Province, Thailand, where it is native, 2009. Photo by Tony Rodd (flickr, Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license).


Photograph showing seed dispersal units of itchgrass. Each unit is cylindrical with a rounded appendage at its lower end. The dispersal units are less than 1 centimeter in length.

Dispersal units (seed-containing structures) of itchgrass. Each dispersal unit has an elaiosome projecting from it (the structures at the bottom of each dispersal unti). Photo by Julia Scher (Bugwood.org photo 5376737, Creative Commons Attribution-NonCommercial-3.0 United States license, image cropped and resized).

What are the impacts of itchgrass?

Itchgrass is a major weed in agricultural environments. It is considered a weed for 18 crops, including the grass crops corn (Zea mays), rice (Oryza sativa), sorghum (Sorghum bicolor), and sugarcane (Saccharum), as well as the major legume crop soybean (Glycine max). It grows in dense clumps, and its presence in agricultural settings often significantly reduces crop yields. Managing itchgrass is often costly.

The hairs on itchgrass are unpalatable and cause severe irritation to most grazers, so animals do not eat itchgrass. The hairs can also irritate the skin of agricultural workers.


Photograph of a corn field that has been infested by itchgrass. The photo shows a field of tall corn with a shorter clump of itchgrass in the center front of the image.
Photograph showing a detail the leaf sheaths of an itchgrass plant. The sheaths have conspicuous white hairs.

How can itchgrass be controlled?

Both mechanical and chemical methods are used to control itchgrass; currently, no biological control methods have been developed for itchgrass management, although several have been studied. No single control tactic is effective by itself, but several control methods used together can be effective.

Most commonly, tilling followed by herbicide application is used as a control. Tilling prior to planting agricultural crops encourages the germination of itchgrass. Once the seedlings emerge, they can be sprayed with herbicide. A variety of herbicides can be used, both before and after itchgrass germinates and emerges. Small clumps of itchgrass can also be removed by hand, although this method is not effective at larger scales.

Certain agricultural practices also control itchgrass, such as implementing a crop rotation or planting cover crops. Crop rotation helps control itchgrass because the weed has closer associations with some crops (such as maize) than others. Planting nitrogen-fixing legumes as cover crop is also a way of controlling itchgrass and restoring nutrients to the soil.


Photograph of a man standing in a field of grass, holding an uprooted itchgrass plant with a gloved hand.

Resources

Articles & reports

Itch grass (458) (Pacific pests, pathogens & weeds - fact): https://apps.lucidcentral.org/ppp_v9/text/web_full/entities/itch_grass_458.htm

Itchgrass, Rottboellia cochinchinensis (Invasive.Org, Center for Invasive Species and Ecosystem Health): https://www.invasive.org/browse/subinfo.cfm?sub=4568

Rottboellia cochinchinensis, Itchgrass (Florida Department of Agriculture and Consumer Services): https://www.fdacs.gov/Agriculture-Industry/Pests-and-Diseases/Plant-Pests-and-Diseases/Noxious-Weeds/Rottboellia-cochinchinensis-Itchgrass

Book chapters

Valverde, B. E. 2003. Progress on Rottboellia cochinchinensis management. In: R. Labrada (ed.), Weed management for developing countries. Food and Agriculture Organization of the United Nations. https://www.fao.org/3/y5031e/y5031e07.htm#bm07

Scientific articles

Lencse, R. J., and J. L. Griffin, J. L. 1991. Itchgrass (Rottboellia cochinchinensis) interference in sugarcane (Saccharum sp.). Weed Technology 5: 396-399. https://doi.org/10.1017/s0890037x0002830x