Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/1/2006
Publication Date: 6/1/2008
Citation: Szabo, L.J., Koike, S.T., Hill, J.P. 2008. Rust. In: Schwartz, H.F, Mohan, S.K., editors. Compendium of Onion and Garlic Diseases and Pests. 2nd Edition. Minneapolis, Minnesota: APS Press. p. 41-44.
Technical Abstract: Rust was first found on onions in England in 1809. It occurs throughout the world, including Europe, Australasia, Asia, the Middle East, Africa, South America, and North America. Rust has been found on most Allium species including chives (Allium schoenoprasum), garlic (A. sativum), leek (cultivated leek, A. porrum; wild leek, A. ampeloprasum), and bulb onion (A. cepa). Worldwide, rust has caused significant losses to garlic, leek, and onion production. The causal agent of rust on garlic, leek, and onion is Puccinia allii Rudolphi. P. allii is a macrocyclic, autoecious rust, producing up to five spore stages on a single host. An altered form of the life cycle occurs in which only uredina and telia are observed. In this case, the rust is homothallic. This shortened form of the life cycle is referred to as hemicyclic and has been found in North America, Japan, and Europe. The taxonomic classification of P. allii has been in flux due to variation in host range, morphological characteristics, and life cycle form. The current classification of P. allii is considered a species complex rather than a single species and includes P. porri, P. mixta, Uromyces ambiguus, P. blasdalei, and U. duris. At present two members of this species complex have been clearly defined and are represented by the North American collections from garlic and Middle Eastern collections from leek. Rust is an airborne pathogen, and inoculum sources are from infected plant material such as diseased crop residue, volunteer plants, and older diseased plantings. Crop rotation, separation of onion and leek crops, and management of weeds belonging to the onion family help reduce disease incidence. If environmental conditions favorable for disease development occur, multiple fungicide applications will be necessary to manage the disease. For some allium crops, resistant cultivars are available.