Hollyhock Rust
Puccinia malvacearum
This infected plant is Desert Globe Mallow, Sphaeralcea ambigua, a member of the Malvaceae. 11 July, 2015, at Phoenix, Maricopa Co., Arizona. Underside of leaf.
Desert Globe Mallow
During the spring of most years the Sonoran Desert is subject to an extended drought from April until the summer rains arrive in July. During this time many shrubs are deciduous, losing all or most of their leaves. Therefore, fungal infections like this one might not have enough time to mature on the leaves. In cityscapes and perhaps natural riparian zones the plants keep their leaves which might promote the infection cycle. There are many species of Puccinia - this one is better known because it also affects the popular garden plant Hollyhock.