melanose or canker of citrus

例句：

1. 1.The melanose on the grapes is a sign that they are ripe.
   葡萄上的黑斑是它们成熟的标志。
2. 2.The canker of citrus is a serious disease that affects many types of fruit trees.
   柑橘黑斑病是一种严重的疾病，影响了许多种类的果树。
3. 3. To prevent the melanose, it's important to maintain good sanitation in the orchard.
   为了防止黑斑病，果园要保持良好的卫生条件。