Disease: Watermelon Fruit Blotch (Bacterial Fruit Blotch)Pathogen: Acidovorax avenae subsp. citrulliHost: watermelon, pumpkin, canteloupe
A dark olive green stain or blotch on the upper surface is the characteristic symptom of fruit blotch of watermelon, a bacterial disease. The first symptoms of the disease appear as water-soaked areas on the fruit surface that rapidly expand to cover a larger area of the melon. Leaf tissue also can be affected; symptoms are small, dark brown, angular spots. Also, symptoms may not appear on the surface of the fruit, but the inner portion of the watermelon may appear as the one above. This disease is seed-borne, so it is best to use pathogen-free seed if possible. The bacterial pathogen is not harmful to humans, but it can certainly ruin a Fourth of July picnic!