Stem Pitting Fruit Pathology Penn State Department of Plant Pathology Jim Travis, Jo Rytter and Ken Hickey Prunus Stem Pitting Prunus stem pitting is an important disease of all stone fruits. It is also called prune brownline and constriction disease. Apple union necrosis and decline is caused but the same virus and nematode vector as is Prunus stem pitting. In general, affected trees are stunted and look unthrifty.
Foliar symptoms develop in late summer after harvest but prior to normal defoliation.
Leaves on affected trees cup upward along the midrib, turn various shades of yellow through red to purple and then begin to drop prematurely. Care must be taken in diagnosing stem pitting. These symptoms indicate that root problems exist and are not always diagnostic of stem pitting. Other factors can be involved such as root rot, nutrient deficiencies, herbicide damage, mouse girdling and various injuries. The following season, the trees will appear weak, growth will be stunted and a girdling of the trunk will result.