First report of Xylella fastidiosa in continental China
In China, walnut leaf scorch was first reported from Juglans regia in 2012 in Hotan (Xinjiang province). Symptoms include brown spots on the leaflets that further spread along the leaf margins, in a flame-like pattern. The scorched areas curl inward with a yellow halo. In severe cases, the leaves dry up and shrink, affecting the entire tree.
Xylella fastidiosa (EPPO A2 List) was detected by PCR in walnut (Juglans regia) leaf samples from three locations in Xinjiang. Koch's postulates were completed. The subspecies involved was identified as X. fastidiosa subsp. multiplex.
According to the EPPO Secretariat, this is the first confirmed record of X. fastidiosa in continental China. The authors note that X. fastidiosa had been found infecting grapes in Shaanxi (Chu, 2001) but the EPPO Secretariat could not access this publication and could not retrieve additional records of the bacterium in China. It can be noted that X. fastidiosa occurs in Taiwan.
Sources
Chu YJ (2001) Pierce's disease of grape and control techniques. Yantai Fruits 4, 11–12 (in Chinese).
Guo T, Wang S, Pan C, Sattar A, Xing C, Hao H, Zhang C (2024) Evidence of the involvement of Xylella fastidiosa in the occurrence of walnut leaf scorch in Xinjiang, China. Plant Disease. https://doi.org/10.1094/PDIS-07-23-1430-PDN