Puccinia rust on Vinca. aka: Periwinkle Rust Sunshine Hill area, Tuolumne County, California.
For information on Puccinia rust, see: https://pnwhandbooks.org/plantdisease/host-disease/vinca-spp-periwinkle-rust
from that website:
Cause The fungus Puccinia vincae has been found in all PNW states. An alternate host is not needed for this autoecious rust. The frequent occurrence of the rust on new leaves and other factors suggest that the rust may be systemic in the plant.
Symptoms Leaves turn chlorotic with inconspicuous leaf spots on the upper surface of the leaf. Lower leaf surfaces have dark uredinina where telia are also produced. Heavily infected leaves may curl upward and shoots typically do not flower. Poor winter survival once a bed of plants is infected in western Oregon.
- Remove and destroy infected plants or plant parts.
- Avoid overhead irrigation or apply such that plants are not wet for extended periods of time.
- Pageant at 12 to 18 oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Phyton 27 at 1.3 to 2 oz/10 gal water. Group M1 fungicide. 48-hr reentry.
- Terraguard SC at 4 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Zyban WSB at 24 oz/100 gal water. Not to be confused with the smoking cessation drug. Group 1 + M3 fungicide. 24-hr reentry.
Reference Hernández, J.R., Palm-Hernández, M.E. and Tidwell, T. 2002. First report of Puccinia vincae on Vinca spp. in California. Plant Disease 86:75-75.
Thanks to Farm Advisor Scott Oneto for the ID!