Badly infected leaves become very crinkled, distorted, and stunted. Fruit severely attacked when very small often become misshapen. Scab can be particularly severe on Temples and lemons and often troublesome on Murcotts, Minneola tangelos and grapefruit. Scab on foliage Figure 4. They feel like sandpaper when touched.
Pustules are larger and more raised on grapefruit than on round oranges and tangerines.
The pustules often form in a tear-streaking pattern caused by water flowing down the surface and carrying spores. Fruit becomes resistant to infection about 12 weeks after petal fall. Spores of Diaporthe citri arise from fruiting structures that develop on twigs that have recently died. The spores are moved to fruit via rain. Infected fruit does not serve as an inoculm source .