penicillium expansum causes blue mould disease in a broad range of hosts including apples, and is one of the most destructive pathogens of pome fruit, reaching up to 50% of stored fruit losses. this pathogen is a necrotroph and requires a wound in the eidermis to enter fruit tissue and initiate infection. conidia of penicillium species are ubiquitous in the atmosphere of packinghouses, even in production areas where the most advanced storage technologies are used. therefore, mechanical injury caused during harvesting and postharvest handling provides an optimal locus for infection.