Control Methods for 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 damages Picea asperata (dragon spruce), Picea purpurea (purple cone spruce), Picea likiangensis (Likiang spruce), Picea brachytyla var. complanata (oil wheat hanging spruce), Picea jezoensis (Yeddo spruce), Picea schrenkiana (Schrenk spruce), ** spruce and others.

Symptoms: The disease damages the upper surface of female cone scales. Infected scales are twisted, rolled back and disorganized. On the upper surface, many purplish-brown small spheres are produced, arranged in a single layer; these are the aeciospore pustules of the pathogen. Sometimes aeciospore pustules also form on the underside of the scales.

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

Disease cycle: The pathogen is a rust fungus with a long-cycle life history. It overwinters as teliospores on fallen bird cherry leaves. The following year, when spruce cone scales open for pollination, the teliospores germinate and produce basidiospores that invade the scales. One week later, flat, blister-like spermagonia appear on the scales. In late summer, spherical, purplish-brown aeciospore pustules appear on the scales. The aeciospore pustules do not rupture in the same year; the following year, the aeciospore pustules split open and release aeciospores, which are spread by wind to bird cherry leaves. The aeciospores germinate on bird cherry leaves, invade the leaf tissue, and then produce uredinia and urediniospores. The urediniospores can cause multiple secondary infections. In autumn, telia and teliospores are produced on the upper surface of infected leaves. When spruce is close to bird cherry, the incidence rate is high and the disease is severe.

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 and pollination occurs, spray 300-500 times diluted fenarimol.