Summary In summer of 2004, pycnidia of Diplodia pinea were observed on cones of Pinus resinosa that had matured and opened during previous years, but had been retained in canopies of trees at a mature red pine plantation in southern Wisconsin. Surveys during the winter and early summer of three consecutive years (2005–2007) to determine incidence and abundance of D. pinea conidia on cones of different ages in this stand. Cones from each age class consistently bore pycnidia with conidia of D. pinea. Although cones collected in June of the year after their maturation tended to yield more D. pinea conidia than older cones, large numbers of conidia were obtained from cones even 3 years after maturation. Perennial availability of inoculum due to persistence of D. pinea on cones of several ages in the overstory or in adjacent stands should be considered when regenerating red pine in areas where this pathogen is known to be present.