Symptom Identification and Control Methods for Carnation Rust

[Pathogen] Uromyces caryophyllinus (Schrank) Wint., belonging to the fungal subphylum Basidiomycotina, genus Uromyces. It is a heteroecious rust fungus.

[Symptoms] The disease mainly damages leaves, and also damages stems and calyx. The affected parts initially show pale small raised spots, which later turn yellow around the edges. In severe cases, leaves and stems become distorted. During the growing season, brown small powdery masses appear on the underside of infected leaves or on stems and calyx lobes; these are the uredinia of the pathogen. In autumn and winter, black small powdery masses appear at the affected sites; these are the telia of the pathogen.

[Disease Cycle] The pathogen overwinters on infected plants. The following spring, teliospores germinate to produce basidia and spores; basidiospores infect Euphorbia plants, forming spermogonia and aecia on the leaves. After aeciospores infect carnations, they form uredinia on them; urediniospores spread by wind or water and cause reinfection. Telia are produced at the end of the growing season.

[Epidemic Characteristics] High temperature and high humidity favor the occurrence and epidemic of this disease.

[Control Measures]

A. Strengthen ventilation in the greenhouse and keep the temperature at around 15°C as much as possible; a cool and dry environment favors carnation growth but is unfavorable for rust development.

B. When propagating and raising seedlings, cuttings should be taken from disease-free plants.

C. Avoid sprinkler irrigation that favors pathogen spread; if sprinkler irrigation is needed, it should be done on sunny days.

D. During the disease period, spray with 50% oxycarboxin 1000-fold solution or 65% zineb 600-fold solution, or apply the chemicals in proportion through a modern irrigation system.