Star crack, a virus disease, develops on apples in Europe, the United States, Canada, and New Zealand. Symptoms vary widely, depending on the apple variety and perhaps the stage of development at which the fruits are affected. In England the disease occurs most frequently on Cox's Orange Pippin, causing little distortion of the fruits. On this variety the corky, star-shaped cracks, from which the disease is named, develop to some extent on the cheeks, but mainly on the calyx end of the fruits.
On Golden Delicious grown in the State of Washington, affected fruits are badly distorted, and the cracks may develop on any area (see photo). Varying amounts of rough, cork-like tissues may be found on the surf ace as a result of the healed cracks.
The disease must be controlled in the orchard by using virus-free bud and nursery stock. Consult your State agricultural extension service or experiment station.