perennial canker

例句：

1. 1. The disease is a perennial problem in the region.
   该地区的这种疾病是一个长期存在的问题。
2. 2. The farmer has been dealing with this perennial canker for years.
   这位农民多年来一直在处理这种多年生根瘤病。
3. 3.The farmers are trying to prevent the spread of this perennial canker through proper irrigation practices.
   农民们正试图通过适当的灌溉实践来防止这种多年生根瘤病的传播。