Symptoms and Signs
Aspergillus rot infections begin most commonly in the orchard following rain during flowering and early fruit development. The fungus may grow inside the fruit without external symptoms, but external decay symptoms are more commonly seen with Aspergillus fruit rot than with Alternaria fruit rot. External decay is usually close to the calyx of fruit, with the rind of the fruit slightly off-color (e.g., paler red) and may show some yellowish to brownish-red discoloration. Inside the fruit there is black powdery sporulation and a brownish decay of the arils. Black sporulation may also show on the rind and on the cracks of the fruit.
Comments on the Disease
Colonization by Aspergillus niger is often associated with insect infestations, such as feeding by hemipterans, or other factors that cause fruit injury or cracking (e.g., bird pecking, sunburn, overwatering, and russeting). The pathogens overwinter in plant debris, in or on the soil, and in mummified fruit. Airborne spores can be carried into fruit wounds with soil dust.
Because the fruit crown covers the blossom tissues, the use of preharvest sprays are generally ineffective.
- Use good orchard management practices, such as dust control and sanitation (removal of old fruit and dead branches), to reduce the pre- and postharvest incidence of disease.
- Control insect pests such as filbertworm, leaffooted bugs, and carob moth that feed on the fruit, enabling pathogen entry.
- Gently shake the tree at the time of harvest to drop infected, but healthy-appearing, fruit to the ground.
- Avoid water stress and over watering that may result in fruit cracking.
- Thoroughly sort and grade pomegranates for discoloration and cracking to reduce the chance of packing diseased fruit.