Grass weeds are, in general, more of a problem during the summer than they are at other times of the year. There are more than 25 annual grass species that are found here during the summer although only about 10 are common. Most of these look very similar at early growth stages and identification can be difficult. There is a tendency to lump them all together and call them water grass, jungle rice barnyard grass or several other names. There are differences between them, however, and it is important to accurately identify them at early growth stages. This is important because many of them respond differently to herbicides and have different growth habits. For example, sprangletop is only controlled by the highest rates of Select (clethodim) and generics of this herbicide and missed by all of the other selective postemergence herbicides like Poast and Fusilade and sandbur is tolerant to all of them. By the same token, sandbur and sprangletop can over winter, come back from crowns and not be controlled by preemergence herbicides applied in the spring while most other summer annual grasses die in the winter and the seed can be controlled with herbicides in the spring. There are just 6 genera and 12 species of summer annual grass that are common here. These include echinochloa (water grass and barnyard grass), leptochloa (red sprangletop and mexican sprangletop), eriochloa(southwestern cupgrass and prarie cupgrass) , cenchrus (field sandbur and red sandbur), setaria (green foxtail and yellow foxtail), and chloris (feather finger grass and truncate finger grass). Visit the publication Summer Annual Grass Identification, which contains pictures and descriptive characteristics of each of these species.

To contact Barry Tickes go to: btickes@ag.arizona.edu.

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.