Symptoms and Control Methods of Spruce-Bird Cherry Cone Rust

Spruce-bird cherry cone rust occurs in Inner Mongolia, Jilin, Heilongjiang, Sichuan, Yunnan, Tibet, Shaanxi, Gansu, Qinghai, ** and other places in China. The disease affects Picea asperata, Picea purpurea, Picea likiangensis, Picea brachytyla var. complanata, Picea jezoensis, Picea schrenkiana, ** spruce, etc.

Symptoms: The disease affects the upper surface of the scales of female cones. Infected scales are twisted, recurved and disorganized. On the upper surface, many small purple-brown spherical bodies are produced in a single layer; these are the aeciospore-bearing structures (aecia) of the pathogen, and sometimes aecia are also produced on the lower surface of the scales.

Pathogen: The pathogen is Thekospora areolata (Fr.) Magn., a fungus belonging to the Basidiomycota, Teliomycetes, Uredinales, and the genus Thekospora.

Disease cycle: The pathogen is a rust fungus with a long-cycle life history. It overwinters as teliospores on fallen leaves of bird cherry. In the second year, when the scales of spruce cones open for pollination, the teliospores germinate and produce basidiospores that infect the scales. One week later, flat, blister-like spermogonia appear on the scales. In late summer, spherical, purple-brown aecia appear on the scales. The aecia do not split open in the same year; in the second year, the aecia split open and release aeciospores, which are spread by wind to bird cherry leaves. The aeciospores germinate on bird cherry leaves, infect the leaves, and then produce uredinia and urediniospores. The urediniospores can cause multiple secondary infections. In autumn, teliospore masses and teliospores are produced on the upper surface of infected leaves. The closer spruce is to bird cherry, the higher and more severe the disease incidence.

Control: (1) Cut down bird cherry and treat with glyphosate, or spray herbicides such as 2,4-D butyl ester; this has a certain effect. (2) During the period when spruce cone scales crack open for pollination, spray 300-500 times diluted Fenxiuning.