Unlike scab, vein spot only affects the leaves. Lesions of vein spot disease develop on veins of leaflets and are characteristically dark brown to black. Severely infected leaflets shed soon after symptoms are observed. The fungus overwinters in fallen leaves beneath the tree. Fungicides and sanitation procedures will control this fungus.
Fungicides applied for scab control are also effective against the vein spot fungus.
This disease occurs mainly on low vigor trees. It overwinters in infected leaves on the orchard floor. Symptoms first appear on the under surface of mature leaves in early summer as small olive-green velvety spots. By midsummer, black pimple-like dots are visible in the spots. When severe, infected leaflets are killed, causing leaf shed in late summer or early fall.