Figure 7: Apple in the early stages of blue mold rot: the pathogen entered via an injury. Initially light-brown, glassy changes to the skin, followed by the eruption from the softened flesh of gray-white mold tufts bearing green, dusty spores. The pathogen Penicillium expansum (a penicillin mold) can only attack ripe fruits. The intense moldy taste associated with blue mold rot is particularly unpleasant.