Anthracnose of Cucurbits

Anthracnose of Cucurbits (Colletotrichum orbiculare) is a plant pathogen of melons and cucumber. The disease occurs worldwide, but is usually of minor importance in arid regions. In areas of high humidity, however, C. orbiculare can be very damaging.

Symptoms
Initial symptoms appear as irregularly shaped water-soaked leaf lesions that soon turn chlorotic. Lesions can expand to greater than 1cm (⅓in) in diameter and turn tan to brown in colour. On watermelon such lesions are darker and appear brown to black. Extensive lesion development will cause the leaf to buckle and become distorted. Lesion tissue dies, cracks and falls out. Lesions can also occur on petioles and stems and start out as elongated, oval to diamond-shaped, water-soaked lesions that later turn tan to brown. Stem lesions can be covered with the minute black fungal structures (acervuli) and pink spore masses that are exuded by these fruiting bodies. Clear brown exudates can also collect on these stem lesions. Fruit symptoms are circular water-soaked areas that later become dark brown to black sunken lesions. If high humidity and water are present, acervuli of the pathogen will grow in the fruit lesions and exude gelatinous pink spore masses.

Prevention
Plant certified disease-free seeds. Plant resistant varieties, where available. Practice crop rotation with non-legumes such as cereals.