Penicillium includes some of the most economically important fungi. Biodeterioration and food spoilage, caused by some of the species of Penicillium are known. Some species are toxigenic and can cause human or animal diseases. Some species are specialized, such as fruit pathogens (e.g. P. digitatum, P. expansum, P. italicum, P. oxalicum, P. solitum and P. ulaiense. The most common and serious postharvest diseases of citrus fruits are green and blue moulds, caused by Penicillium digitatum and P. italicum, respectively.