Gummy Stem Blight

Gummy stem blight, caused by the fungus Didymella bryoniae, is a common disease of all major cucurbits and is present wherever they are grown.  A wide range of foliar symptoms occurs on cucurbits, which can make diagnosis difficult. Gummy stem blight causes ovate stem and vine cankers, usually starting near the nodes, with a characteristic brown gummy exudate. Within advanced lesions on dead tissue, small black fungal fruiting bodies, known as pycnidia, can be seen with a 10x hand lense. Leaves can exhibit dark brown circular spots starting at margins and rapidly spreading to entire leaf. These foliar lesions can vary in color from light brown to nearly black. Black rot infected fruits show small water-soaked spots that advance into large brown spots, sometimes also exhibiting the brown gummy secretion as found in stems.