Blue mould rot in Citrus fruits is caused by

Blue mold rot in Citrus fruits is caused by Penicillium italicum. The species that most commonly cause postharvest spoilage of citrus fruit. The fungi gain entry if the fruit is damaged during handling and storage and then decay can spread from fruit to fruit.
Blue mold and green mold are the primary post-harvest pathogen of citrus, and there are few effective control measures for sour rot, sour rot could be controlled by a low-temperature environment, but the chilling injury still causes major bottlenecks.