黑变病

例句：

1. 1. The black spot on the apple tree is a sign of poor health.
   苹果树上的黑斑是健康不佳的迹象。
2. 2. The farmers are worried about the spread of black spot disease in their crops.
   农民们担心黑斑病在他们的作物中传播。
3. 3. To prevent black spot disease, it's important to maintain good hygiene practices.
   为了预防黑斑病，保持良好的卫生习惯很重要。