Mulberry fruit spot

The disease is caused by the ascomycete fungus Ciboria carunculoides, a specific pathogen that targets the fruiting bodies of mulberry trees. This fungus is responsible for a condition often called "popcorn disease" or mulberry fruit rot, which can significantly damage the harvest quality.

The primary host for this pathogen is the mulberry tree (Morus species). The infection specifically attacks the developing syncarps (mulberry fruits). While it does not kill the tree itself, the impact on fruit production is severe, rendering the berries unmarketable and unsuitable for consumption due to the fungal structural changes.

The symptoms of the infection appear as the distortion and hypertrophy of individual drupelets within the fruit cluster. Infected berries turn greyish, harden significantly, and become covered in a white fungal mycelium. Eventually, the entire fruit shrivels and hardens, turning into a blackened, mummified structure that often persists on the tree branches.

The development and spread of Ciboria carunculoides are heavily dependent on environmental conditions, particularly high humidity and mild temperatures during the flowering stage. The fungus survives the winter as sclerotia within mummified fruits. In early spring, these sclerotia produce small, cup-shaped apothecia that release spores, which are then dispersed by wind and rain to infect new blossoms.

Management and prevention focus primarily on orchard sanitation. It is essential to collect and destroy all mummified fruits before they fall to the ground to break the disease cycle. Cultivating the soil under trees during early spring can help bury and inhibit the development of the fungus's fruiting bodies. In areas with high disease pressure, preventative fungicide applications during the bloom period may be required.