John H. Brock
College of Integrative Sciences and Arts, Arizona State University Polytechnic, Mesa, Arizona, USA
Seven alien invasive annual grasses are found in the southwest region of the United States and northern Mexico. All of these annual grasses germinate with autumn and winter rainfall. They begin rapid growth as temperatures increase in February and March and reach peak standing crop late in the spring, either May or June depending on their distribution by elevation. When in the vegetative mode, they are consumed by grazing animals, but when they produce seed heads, grazing essentially ceases. Their seeds are easily dispersed and in general have about a three-year life in the seed bank. All of these species were introduced from Europe/Asia. The dominant genus is Bromus and includes: Bromus rubens syn. B. madritensis (red bromegrass), B. tectorum (downy bromegrass), B. carthicus (rescue grass), B. japonicus (Japanese bromegrass), and B. diandrus (ripgut brome). Schimus barbatus (Mediterranean grass) a short lived small grass is found primarily in the warm deserts. Avena fatua (wild oats) provides good forage in the spring and is currently found at elevations of less than 1,500 m. All of these grasses compete with native vegetation and can promote wild fires. Management of these species includes targeted grazing by domestic livestock, prescribed burning, mowing and the use of both pre and post emergence herbicides.