Roses in the garden can be infected with a variety of bacteria, fungi, and viruses, leading to diseases like powdery mildew and rust. Roses may also be damaged by nutrient deficiencies and other environmental problems.
Our Pest Notes: Roses: Diseases and Disorders was recently updated by University of California experts John Karlik, Deborah Golino, and Maher Al Rwahnih. This free publication provides an integrated approach to managing rose problems that includes careful variety choice, proper irrigation, correct pruning, and sanitation. Although some rose enthusiasts might consider regular application of fungicides a necessary...
[From the April-May 2016 issue of the UC IPM Green Bulletin]
A downy mildew caused by the fungus Peronospora mesembryanthemi has recently been confirmed by the USDA-APHIS from a red apple ice plant (Aptenia cordifolia) sample collected in San Diego. Since this first finding in San Diego County in summer 2015, the disease has spread to Orange, San Bernardino, and Ventura counties and is now found in the Goleta area in Santa Barbara County.
Peronospora mesembryanthemi was first reported from South Africa and.../span>