Chestnuts often rot during storage due to fungal infection. This study found that oil extracted from perilla leaves, particularly a compound called perillaldehyde, effectively prevents the fungus Botryosphaeria dothidea from growing. The antifungal compounds work by breaking down the protective layers of the fungal cells, causing them to leak and die. When applied to stored chestnuts, this natural oil significantly extends their shelf life without harming human health.