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Relationship Between Stem Pitting in Peach and in Other Prunus Species. Srecko M. Mircetich, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705; E. L. Civerolo, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705. Phytopathology 62:1294-1302. Accepted for publication 23 May 1972. DOI: 10.1094/Phyto-62-1294.

Differential expression of stem pitting symptoms in various naturally infected species of stone fruits was observed. However, the stem pitting (SP) causal agent was readily graft-transmitted by cross inoculation of different Prunus spp. Stem pitting symptoms in inoculated indicator plants are similar to those in the same Prunus sp. naturally pitted regardless of the donor Prunus spp. Apparently, stem pitting in different Prunus is caused by the same, or related strains of the same, causal agent. Natural spread of stem pitting was demonstrated by annual surveys in densely planted apricot and sour cherry seedling orchards. Spread in the field may occur from an infected tree to trees of the same or different Prunus sp. The disease usually spreads from infected to adjacent trees with no random occurrence of newly infected trees in the orchards. A virus recovered from soil of peach, nectarine, and apricot orchards infested with stem pitting was serologically related to the type culture of tomato ring spot virus and to two isolates of peach yellow bud mosaic virus. The same virus was also recovered from apricot, European plum, and Nanking cherry seedlings inoculated with root chips from naturally infected peach and apricot orchard trees. However, we found no correlation between the presence of this virus in soil and stem pitting in orchard trees, nor consistent association of this virus with experimentally infected-pitted indicator plants. Apricot seedlings planted to sites of naturally pitted peach orchard trees developed stem pitting within 5 months.