Watermelon stem lesion with gummy exudate, a symptom of gummy stem blight. Circular lesion of gummy stem blight in watermelon with concentric rings.įigure 2. You can refer to the Mid-Atlantic Commercial Vegetable Production Recommendations for a list of recommended fungicides. Currently, DMI, AP, SDHI, and PP fungicides (tebuconazole, difenoconazole, cyprodinil, fluopyram, fludioxonil, etc.) are relied upon with pre-mixtures common and tank mixed with chlorothalonil or mancozeb to manage fungicide resistance in gummy stem blight. On older leaves in the field, irregular brown to black. Often, infected transplants will have lesions on the the stem (Image 2). Early infection usually develops from contaminated seed and can be visible on transplants (Image 1). In the US, the disease has shown resistance to boscalid, azoxystrobin, thiophanate-methyl, penthiopyrad and low levels of resistance to tebuconazole. Early symptoms are round black, wrinkled spots on young leaves and dark sunken areas on stems. Fruit is rarely affected, but loss of foliage may affect yield and fruit quality. Gummy stem blight causes lesions on stems and leaves. Gummy stem blight (GSB) is caused by the fungus Didymella bryoniae (asexual state as Phoma cucurbitacearum or Ascochyta cucumis) and previously known as. Optimal conditions for gummy stem blight infection in watermelon is 75☏ temperature and prolonged moisture with leaf wetness lasting 1-10 hours.įungicide resistance is an important consideration for gummy stem blight. First Report of Gummy Stem Blight Caused by Didymellabryoniae on Watermelon and Conrmation of the Disease on Pumpkin in T anzania. Gummy stem blight (also called black rot) is one of the most serious foliar diseases of muskmelon and watermelon in Indiana. Gummy stem blight can be confused with anthracnose but the leaf lesions of anthracnose are irregularly shaped in watermelon and the stem cankers are spindle-shaped. Early symptoms on fruit are circular and greasy in appearance but eventually will coalesce and become brown/black in color. Black rot of watermelon fruit only occurs if the vines are severely infected. A diagnostic sign of gummy stem blight is the black fruiting bodies (pycnidia), which can be found in the lesions. Stem cankers can girdle the stems and cause wilting a few weeks after infection. Symptoms on watermelon vines often include cracking and a gummy ooze, but this can also occur in anthracnose and low pH conditions.
This pathogen was identified within a very short period of time by the Real-Time PCR. bryoniae was reliably identified using morphological and molecular characterization.
Leaf lesions in watermelon often start at the leaf margin and are brown, circular, and have concentric rings. bryoniae as the causal agent of Gummy Stem Blight (GSB) disease of watermelon (Citrullus lanatus) in Turkey. Gummy stem blight can cause symptoms on the leaves, stems, and vines and is also called black rot when fruits are infected. It can be introduced from infected seed or seedlings, highlighting the importance of greenhouse and field sanitation. Gummy stem blight (GSB), a common disease of all major cucurbits, is caused by the fungus Didymella bryoniae. and can occur on cucurbit crops and seedlings. Jake Jones, Extension Agriculture Agent, Kent County Stem blight is caused by Stagonosporopsis spp.
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