Didymella bryoniae only occurs on Cucurbitaceae. Gummy stem blight is evident in various ways, such as leaf lesions, stem cankers, wilt and black rot of fruits. Pale brown or grey lesions on the leaves, petioles and stem are typical symptoms of an infection. Circular lesions on stems often grow into elongated cankers (starting at the nodes), which produce an amber-coloured gummy exudate. Leaves turn yellow and may die back, and sometimes even the whole plant will wilt and turn brown.
Didymella bryoniae infects fruits of cucumber, melon, courgette, pumpkin and gourds and the initial symptoms are spots on the fruit surface. Symptoms vary in different crops. Over time, spots turn black and can penetrate the skin (lesion). These lesions form entry points to the fruit for other organisms and can cause internal fruit rot, resulting in the whole fruit becoming a watery mass enclosed by the skin.
The fungus grows at temperatures of between 7 °C and 33 °C. The optimum temperature range for disease development is 20°C tot 28°C. The presence of moisture is essential to fungal growth.
Didymella Bryoniae occurs worldwide. If the disease is not controlled at an early stage, it is very difficult to stop it from spreading.