Causal Agent: (fungus – Macrophomina phaseolina)
A water-soaked lesion develops around the crown of the plant, followed by the appearance of an amber-colored ooze at the surface. This area becomes dark brown, dried and cracked. Small black fungal structures (microsclerotia) are then formed in this area. A dark ring is visible beneath the outer layer when a cross section is cut through the canker. Infected plants have yellow leaves and die soon after symptoms are observed.
The damage is most severe when melons approach maturity. There are no effective controls for the fungus. Altering the irrigation program to prevent water stress may alleviate the problem.
Note: Charcoal rot image from the Cucurbit Problem Solver.