Rust, caused by the fungus and is the most common foliar disease of carnation in Hawaii. The first symptoms on leaves, stems, or flower buds are small, slightly raised blisters that eventually rupture, forming pustules filled with powdery reddish-brown spores. A yellow margin surrounds the pustules and, when infections are severe, entire leaves turn yellow and die. Stems may be girdled when several pustules develop around the shoot, resulting in decreased flower production and quality. Plants may be attacked at any stage of development. Disease is favoured by cool nights alternating with warm humid days. This induces dew at night and the formation of a film of water on the leaf surface. Because rust spores require free water for nine to 12 hours on the plant surfaces to germinate and infect, this disease is most severe in open air culture and in plastic film greenhouses, where dew formation is common.
How rust disease causes damage in carnation?
