The flesh of nectarines first becomes brown, with white fungal structures developing on the edges of the lesions. As decay develops, the white structures are covered with green-blue spore masses. The lesion is soft and watery, with a defined margin. Penicillium expansum and other species are causal pathogens.
The skin and flesh of the infected fruit tends to disintegrate upon touch. The spore covered lesioned area can often be scooped out, parting from the supposed sound tissue. Penicillium rot is also seen as a part of the ‘soft tissue’ rot pathogens, with development rapid once the fungus has established. Like Rhizopus rot, initial infections are mostly associated with injuries.