New method devised to save Xizang's poplar trees from canker

Chinese scientists have successfully developed an integrated green control strategy to combat canker disease affecting poplar trees in the Qinghai-Tibet Plateau. They have achieved a sustained disease control rate exceeding 80 percent in field trials over a one-year period.

The technology's future industrialization is expected to significantly bolster plantation forest development, thereby enhancing ecological resilience and strengthening the carbon sink capacity of the high-altitude region.

Poplar trees are the dominant species in the area's re-establishment efforts, accounting for 45 percent of the total planted forest area in the Xizang autonomous region.

"Plantation forests play a critical role in restoring ecological balance in the Qinghai-Tibet Plateau, with poplar trees being the dominant species," said Zhang Gengxin, a researcher from the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences.

Zhang highlighted the significant role of poplar trees in sand fixation and carbon sequestration. A related study confirmed that the carbon sequestration capacity of plantations along the Yarlung Zangbo River reaches 20 to 30 metric tons per hectare, comparable to the national average, demonstrating their potential as carbon sinks.

However, the extreme environment — characterized by low temperatures, drought and intense ultraviolet radiation — makes these trees highly susceptible to canker disease.

"Caused by fungal pathogens transmitted via wind, rain, and insects, this disease can lead to bark necrosis, branch breakage, and even whole-tree mortality," Zhang added.

During the three-year project, the research team investigated approximately 35 hectares of poplar trees across Xizang to understand the disease's pathogenic mechanism. They developed a biocontrol agent by isolating antagonistic bacteria with disease-resistant properties and growth-promoting strains from the bark of infected trees. This agent demonstrated high efficacy in suppressing the disease in both laboratory and field inoculation trials.

The research further revealed that an integrated control method was most effective when combined with physical control techniques, such as trunk whitewashing with calcium carbonate and pruning of diseased parts. In demonstration forests in Shannan and Lhasa, this comprehensive approach, which combines the biocontrol agent with physical methods, achieved a sustained disease control rate exceeding 80 percent since being applied last year.

Zhang Sheng, a professor at Sichuan University's College of Life Sciences, emphasized the importance of ecological diversity for the healthy and rapid growth of poplar trees.

"Mixed-species stands and mixed-gender plantations, through resource complementarity and niche differentiation, create a more diverse habitat for soil microorganisms, which can enhance nitrogen and phosphorus availability for poplar trees," Zhang Sheng said, adding that more studies are needed to develop microbial fertilizers in the future.

Liang Eryuan, project leader and researcher from the Institute of Tibetan Plateau Research, noted that the developed biocontrol agent is low-cost compared to existing chemical agents in the market and poses no environmental risks to the fragile plateau.

"Future industrial production could help safeguard the health of poplar plantations in the Qinghai-Tibet Plateau," Liang said. "The diverse disease control methods and growth stimulation methods developed in the project could also serve as sustainable reference models for the green management of plantation forests."

limenghan@chinadaily.com.cn