Taxus chinensis var. syriacus is a common branch disease that affects Yunnan Keteleeria, a type of Chinese fir tree. This fungal disease primarily targets the branches and young saplings' trunks, posing a serious threat to young trees and hindering their healthy growth.
Symptoms of the disease typically appear in the early stages as slightly swollen, spindle-shaped areas on the branches. Over time, these swellings develop into more pronounced, rough-surfaced tumors. In late spring or early summer of the second year, cylindrical rust spores emerge from the cracks in the affected bark. As the spores mature, they rupture and fall off in flaky fragments, releasing large amounts of brown, powdery spores. The growth of the tumors is significantly stunted, leading to thin branches, short and sparse needles, and eventual withering and death of the infected parts. The disease can spread downward along the stems, with new tumors forming beneath the original ones. Rust spores reappear on these new growths the following year, continuing the cycle until the entire branch or even the sapling dies.
The pathogen responsible for this disease is *Perideridermium kunmingense* Ren, which belongs to the Basidiomycota division, specifically the Pucciniomycetes class, and is classified as a rust fungus. It is a single-host parasite, meaning it infects only Yunnan Keteleeria.
The infection process begins when the pathogen enters through the shoots or lateral buds of the tree. Spindle-shaped swellings usually appear in the second year after infection. By the end of the third year, during late spring or early summer, cylindrical rust spores begin to form within the cracks of the tumors. It generally takes 2 to 3 years from initial infection to the production of visible spores. Once an infestation center is established, the disease tends to persist and spread year after year, making it a long-term threat to forest health.
To manage this disease, several preventive and control measures are recommended. First, it is important to reduce the source of infection by removing and destroying infected plants and susceptible seedlings. Second, chemical control methods should be used, such as applying protective fungicides before symptoms appear to prevent infection. Infected trees should also be treated promptly to protect nearby seedlings. Lastly, planting trees using healthy, disease-free seedlings is strongly advised to avoid introducing the pathogen into new areas. These integrated strategies can help minimize the impact of Taxus chinensis var. syriacus and maintain the vitality of Yunnan Keteleeria forests.
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