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Inoculum Sources for Monilinia fructicola in South Carolina Peach Orchards. Frances A. Landgraf, Former graduate assistant, Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29631; Eldon I. Zehr, professor, Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29631. Phytopathology 72:185-190. Accepted for publication 11 May 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-185.

Sources of Monilinia fructicola inoculum near peach orchards were studied during 19791980. Apothecia were found in 1980 under peach and wild plum trees (Prunus angustifolia Marsh and other Prunus spp.). During bloom, few conidia were observed on peach mummies, cankers, and fruit peduncles. Blighted blossoms sporulated profusely in early spring, but sporulation declined as the season progressed. Small increases in sporulation followed rainy periods, and in moist chambers limited sporulation could be induced on 70100% of the blighted blossoms throughout the season. Nonabscised, aborted fruits in the tree and thinned fruits on the ground were important sources of conidia as fruits were approaching maturity. Fruits thinned before pit hardening decomposed quickly, but conidia were produced on some. Fruits thinned after pit hardening often were infected and sporulation occurred on up to 38% of them. Captan and benomyl cover sprays suppressed sporulation on thinned fruits, but sulfur was ineffective. Conidia were produced abundantly on infected wild plum trees throughout the season. Nonabscised, aborted fruits; infected thinned fruits on the ground; and plum infections appear to be the more important sources of the inoculum that affect ripening peach fruits than do blighted peach blossoms.