Which alfalfa disease causes the stem to have a shepherd's crook shape?

The disease that causes the stem of alfalfa to develop a shepherd's crook shape is anthracnose. This fungal disease, caused by species of Colletotrichum, affects various plant tissues, leading to distinctive symptoms. The shepherd's crook shape occurs because the pathogen induces cankers on the stem, resulting in tissue necrosis and abnormal growth. As the infection progresses, the affected areas become weakened, leading the stem to bend and curve in this characteristic manner.

Understanding the symptoms of anthracnose aids in identifying this disease early, allowing for appropriate management strategies to be implemented. Recognizing this distinct growth form is crucial for field diagnosis and can help prevent significant yield losses in alfalfa production. These aspects of anthracnose highlight its impact on plant morphology and emphasize the importance of monitoring for this disease in alfalfa crops.