‘Tree cancer’ weakens roots, poses falling risks

The China Post news staff

TAIPEI, Taiwan — Thousands of trees in Taiwan have contracted brown root rot disease, but it has been difficult to cure them despite substantial government funds allocated annually for their treatment. A total of 23,766 trees around the island were found to have brown root rot disease. They cover an area of 93.1 hectares, equivalent to 3.5 times the size of Taipei’s Daan Forest Park, according to the United Evening News. These sick trees, whose rotten roots can hardly support their trunks, are threats to their neighbors, particularly during typhoons. A 60-year-old banyan tree fell and crushed a gate structure at Tainan’s roughly 350-year-old Confucius Temple — the oldest of such temples in Taiwan honoring the “Supreme Teacher” — in April.

Many schools were forced to, or plan to, remove trees falling victim to brown root disease from their campuses.

The Forestry Bureau allocates about NT$35 million each year to fight the spread of the disease, but efforts have been hampered by the fact that it is difficult to identify sick trees. When trees show symptoms of brown root rot disease — commonly referred to in Taiwan as “tree cancer” — they are already at the “terminal stage.” Efforts to cure such trees are usually ineffective, and chopping them down is usually the only solution, the bureau said. Symptoms of the disease, which is caused by a bacteria infection of the roots, include slow plant growth, yellowing and wilting of leaves, branch dieback, and plant death. The tree’s decline may be fast or slow, possibly depending on the number of roots affected or the location of the decay.

The disease often affects trees in urban areas where they are often planted too close to each other, allowing the bacteria to spread quickly through the root systems.

In Taipei, a total of 6,204 trees with brown root rot disease have been identified since a major outbreak was first reported seven years ago, according to the United Evening News. Most of these trees are located in city parks and along sidewalks. A chemical treatment session for curing a brown root rot tree usually takes six months. If a tree dies of the disease, it must be completely uprooted, and the soil thoroughly disinfected before a replacement can be planted, the Forestry Bureau said.