Cause This disease is caused by a unknown, graft-transmissible agent. All trees exhibiting this serious disease are infected with Apple stem grooving virus, Apple stem pitting virus, and/or Apple chlorotic leaf spot virus. It is not known if the disease is elicited by a combination of one or more of these viruses, a particular isolate of one of these viruses, or a separate, unidentified pathogen. The disease appears not to spread in the orchard. If it does spread, it does so very slowly, and possibly by root grafting.
Symptoms On sensitive cultivars, the fruit will develop deep depressions and distortions that increase in severity as the fruit matures. Cracks may develop in the pits and crevices. Severe fruit symptoms may appear on one or two limbs of an infected tree. There are no leaf symptoms associated with this disease. Symptoms resemble Rosy Apple Aphid injury but can be distinguished from insect injury by the appearance of discolored vascular tissue extending from beneath the pits to the vascular bundles of the fruit. These strands are not associated with insect injury.
- Use only virus-tested (and found to be free of all known viruses) planting and propagation material.
- Remove and destroy infected trees.
Reference Hadidi, A., Barba, M., Candresse, T., and Jelkmann, W. 2011. Virus and Virus-like Diseases of Pome and Stone Fruits. St. Paul, MN: APS Press.