Though primarily known as a disease of apples, this plant pathogen can infect a wide range of hosts, including pears, strawberries, tomatoes, corn, and rice.

Penicillium expansum produces the carcinogenic metabolite patulin, a neurotoxin that is harmful when consumed.

Penicillium expansum has a wide host range, causing similar symptoms on fruits which include apples, pears, cherries, and citrus .

[4] Infected areas are clearly delineated and light brown, and soft decaying tissue can be easily "scooped" out of the surrounding healthy tissue.,[4][1] Spore masses later appear on the surfaces of infected fruit, initially appearing as white mycelium, then turning blue to blue-green in color as the asexual spores mature.

[4] Lesions measure 1–1.25 inches in diameter eight to ten weeks after infection if kept under cold storage conditions.

[7] Penicillium expansum can be identified by its morphological characteristics and secondary metabolites in fruit or in axenic culture.

Conidia can be found in soil, decaying debris, and tree bark, and can survive cold temperatures.

Exposure to conidia at any step of growth, harvesting, processing, shipping, and storage can lead to inoculation and disease.

If the fungus has colonized the fruit with mycelium, the formation of conidiophores occurs on the surface or subsurface of the hyphae.

[19] Considering the size of the apple product industry and the large number of people that may come into contact with infected fruits, control of P. expansum is vitally important.