The fungus can attack fruit on the tree during periods of excessive rains or during irrigation. Infection by the fungus results in decayed areas that are brown, firm and leathery. At first, the fungus cannot be observed on the fruit. Later, a white velvety growth appears on the surface of the fruit, accompanied by a strong fermenting odor. Because the fungus is commonly found in the soil, fruit low on trees often is infected by rain-splashed soil.
Winds can spread the actively growing fungus to fruit in the upper tree.
The fruit must be wet for some time before infection by the brown rot fungus occurs. The best control for brown rot is sanitation during transit and in the packinghouse. This disease is caused by the fungus Diplodia natalensis and often is detected at the packinghouse or in transit. Decay occurs around the stem end and advances in streaks down the side of the fruit. There is no fungal growth on the surface of the fruit.