Disease Note

Kikuyugrass Rust Caused by Phakopsora apoda in Hawaii. D. E. Gardner, National Park Service CPSU, Department of Botany, University of Hawaii, Honolulu 96822. Plant Dis. 68:826. Accepted for publication 2 April 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-826a.

Kikuyugrass (Penniseium clandestinum Hochst. ex Chiov.) is the most widely used pasture grass in Hawaii. Because of its ability to spread and compete aggressively, this perennial species is also an important noxious weed where it has escaped into natural areas. Kikuyugrass is infected with a rust fungus identified as Phakopsora apoda (Har. & Pat.) Mains on the basis of uredinial characteristics, including apically thickened paraphyses, and occurrence on a Pennisetum host. No spore states other than the uredinial have been observed in Hawaii. The disease is widely distributed throughout the islands. Symptoms occur mostly on lower leaves, and infection appears to be enhanced by cool, wet weather and shady conditions. Symptom expression can vary from severe in the shade to mild in full sun only a few meters away. Severe infection causes chlorosis and necrosis, especially of distal leaf portions. Rust material has been deposited at the Arthur Herbarium.