Gnomoniopsis rot

The disease known as Gnomoniopsis rot is caused by the fungus Gnomoniopsis smithogilvyi. This pathogen has emerged as a significant threat to chestnut production globally, causing internal kernel rot that is often difficult to detect during harvest, leading to significant post-harvest losses.

The primary host for this fungus is the European chestnut (Castanea sativa). The infection cycle begins in the orchard, where the fungus infects the developing nuts. It can penetrate the shell through natural openings or physical wounds, and in some cases, it can remain latent until the conditions favor fungal proliferation.

Symptoms of the infection typically include darkening of the shell and the presence of white, cottony mycelium growing within the kernel. When an infected nut is split open, the internal tissue often appears discolored, shriveled, or entirely consumed by the fungal colony. Externally, the nuts may show dark brown or black lesions.

The development and spread of Gnomoniopsis smithogilvyi are closely linked to environmental conditions, particularly high humidity and rainfall during the nut-filling stage. The pathogen survives the winter in leaf litter and mummified nuts left on the orchard floor, which act as a primary source of inoculum for the following season.

The economic impact of this disease is severe, as it leads to high cull rates during sorting and processing. Because infected nuts may appear healthy on the outside, they often reach the market, damaging consumer trust and resulting in economic losses for growers and retailers. Controlling the disease is crucial for maintaining the quality of the chestnut yield.

• Rigorous orchard sanitation by removing mummified nuts from trees.
• Clearing and destroying fallen leaves and debris during winter.
• Monitoring weather patterns to time potential fungicide applications.
• Implementing post-harvest sorting and quick drying protocols.