Bacterial Fruit Blotch

Symptoms

On seedlings: water-soaked lesions on cotyledon undersides that darken and collapse. On fruit: a small olive-green water-soaked blotch on the upper rind that expands rapidly, often cracking and leaking amber ooze as the fruit rots from the rind inward. Foliar lesions are inconspicuous, reddish-brown angular spots along veins, which is exactly why infected transplant houses ship the disease unnoticed.

Management

BFB is managed as a seed problem first. Commercial cucurbit seed lots are screened by seed health assays and seedling grow-outs; transplant houses inspect aggressively because one infected tray contaminates thousands. In the field: avoid overhead irrigation during fruit set, rotate away from cucurbits, and destroy volunteers. No commercial watermelon variety carries strong genetic resistance, which keeps the burden on clean seed, the reason this pathogen reshaped cucurbit seed testing after devastating outbreaks in the late 1980s and 1990s.