Gummy stem blight
Didymella bryoniae
Symptoms:
- Leaf Lesions: Didymella bryoniae is a fungal pathogen that causes leaf blight on cucurbit crops, including cucumbers, melons, pumpkins, and squash.
- Circular Spots: Initial symptoms appear as small, circular lesions on the leaves.
- Necrotic Centers: Lesions often develop necrotic centers with a tan to brown color, surrounded by a darker margin.
- Angular Leaf Spots: As the disease progresses, lesions may coalesce, forming larger, irregularly shaped spots with an angular appearance.
2. Disease Cycle:
- Overwintering: The fungus can survive in infected plant debris, providing a source of inoculum for the next growing season.
- Infection: Infection occurs through spores (conidia) produced on infected debris or within pycnidia (fruiting bodies).
- Spread: Conidia are dispersed by wind, rain, or physical contact, initiating new infections on healthy plants.
- Favorable Conditions: Warm and humid conditions, typical of the growing season, favor disease development.
3. Host Range:
- Cucurbit Crops: Didymella bryoniae primarily affects plants in the cucurbit family, posing a threat to economically important crops.
4. Identification:
- Lesion Characteristics: Identification involves recognizing the circular lesions with necrotic centers and an angular shape.
- Pycnidia: Microscopic examination may reveal pycnidia within lesions, which play a role in spore production.
5. Management:
- Resistant Varieties: Planting cucumber and melon varieties resistant to Didymella bryoniae can help mitigate the impact of the disease.
- Crop Rotation: Avoiding consecutive cultivation of cucurbits in the same location reduces the risk of disease recurrence.
- Fungicide Applications: Fungicides, applied preventively or curatively, can be part of an integrated management strategy.
- Sanitation: Proper disposal of infected plant debris minimizes the overwintering potential of the pathogen.
6. Importance:
- Economic Impact: Leaf blight caused by Didymella bryoniae can result in reduced yields and affect the quality of cucurbit crops.
- Global Distribution: The pathogen is widespread and can be found in cucurbit-growing regions around the world.








