I finally found your website after searching for hours for a picture that matches the disease on my vinca. I am sure that it is Puccinia vincae . Is it necessary to cut it all down to the ground, or just the areas that are infected? I took a sample to my nursery and they told me to cut it all back to the ground and spray with BioAdvanced 3-in-1 Insect, Disease and Mite Control. Since you seem to be more familiar with this....they couldn't even tell me the name...I thought maybe I should get your opinion, Thank you I would send a picture, but can't figure out how to do it...
San Bernardino County California
Without a picture, I can't say for certain, but if you sure of the disease, then we'll will proceed with the management. Cutting the plants to the ground is not necessary, but cutting away all the infected foliage certainly helps (imagine using a . The fungus lives inside the plant before you can see the rust pustules, and once the pustules release their spores there are millions of points of inoculation. However, as a rust, the spores don't survive long on the ground or on any other plant (rusts are VERY selective about their plant hosts), so once you cut away the host plant and destroy it (or bury it in your compost pile, away from the planting site), you can start protecting the plant parts that survive the haircut. The fungicide should be applied to plants, as they emerge, to protect them from further infection. There are very few fungicide products allowed in California (for homeowner application to residential property), but the BioAdvanced 3-in-1 Insect, Disease, and Mite Control product recommended by your local home store does have tebuconazole, an effective fungicide for lots of fungi. You can read the label here: https://bit.ly/2SRh5gO. It also contains insecticide and a miticide, which you may or may not want - something to consider if you do not have any insect or mite issues. BioAdvanced also makes a product that is just the fungicide and an insecticide. Whatever you decide to spray, you will want to look for a fungicide like tebuconazole to protect the new growth for several weeks, applying it as soon as the plants start to regrow, and then again 6 weeks later.