Anderson, Robert C. and Janet Y. Uchida. 2008. Disease index for the rust Puccinia psidii on rose apple in Hawaii. CTAHR Plant Disease publication PD-38, Feb. 2008. College of Tropical Agriculture and Human Resources (CTAHR). Honolulu. 12 pp. illus.
In 2005, Puccinia psidii, an invasive fungus causing guava rust in Brazil, was discovered on potted plants of ohia (Metrosideros polymorpha), on Oahu. This rust infects several members of the Myrtaceae, including rose apple and paperbark, but thus far infections of the common guava have been rare. Urediniospores are the most common type of spores formed by this rust. These bright yellow spores are spherical with tiny spines, easily airborne, and have resulted in distribution of the disease to all major islands in Hawaii. Rose apple (Syzygium jambos) has been devastated in parts of the state exposed to extended periods of moist weather. The disease also occurs in dry areas, but is less severe. Personnel with the federal government, such as the U.S. Forest Service, U.S. Geological Survey, and APHIS, and state agencies, such as the Department of Land and Natural Resources and the Department of Agriculture, are concerned about the extent of the rust's movement in Hawaii. Thus efforts to survey forests, surrounding plant communities, and commercial nurseries were deemed to be of high priority. Hikers and agency field workers can aid in this survey. To gather helpful data, observations of locations of the rust, the disease severity, and the environmental conditions are important. To help organize the disease survey, this disease index on rose apple, the most severely infected host, was prepared. Anyone helping with this survey is sincerely appreciated and should report findings to one of the researchers listed on the back cover. If you observe symptoms other than those described here, or if you have questions, please contact the authors.