Symptoms are most pronounced in spring but may disappear almost completely during summer. Rose leaf curl virus causes leaves to curl downward and die, often with some overall yellowing. There is no known treatment for viruses. Tolerate or destroy infected plants and obtain virus-free stock for future planting. Because mosaic viruses are not vectored by insects but rather are spread through propagation of plant parts, obtaining clean planting stock is the primary management strategy.
Nutrient deficiencies cause specific symptoms.
Nitrogen deficiency causes leaves to yellow and older leaves to drop. Because many California soils have low percentages of organic matter, the nitrogen reserve is typically low and this nutrient should be added as inorganic fertilizer or from organic sources. Micronutrient deficiencies, especially iron and zinc, appear as interveinal chlorosis of new leaves. These elements may be deficient because soils are too wet, are too alkaline, or the content of micronutrients is low in soil types such as sandy loam. Because inorganic forms of iron and zinc form insoluble precipitates in alkaline soils, iron and zinc may be applied directly to foliage.