---

Melanose (fungus - Diaporthe citri)

This is primarily a disease of grapefruit. The first symptoms on leaves are small, circular, dark depressions with a yellow margin. Later, the spots become raised and turn dark brown [Picture]. Leaves turn yellow and may drop prematurely. Raised spots are also found on twigs, which may be killed. Fruit can also become infected. The disease can be severe following rainy periods in the spring, particularly when such periods follow a freeze that has left an abundance of dead twigs.

Melanose is usually controlled by a single fungicide application after bloom or petal fall and before the fruit averages one-half inch in diameter. With a particularly wet spring, a second application may be needed. Citrus should be sprayed for melanose control in the spring following a freeze. Chemical control efforts in heavily infected orchards may need to be combined with supplemental pruning to reduce the quantity of the pathogen.

This fungus also infects fruits. Spots on the fruit are at first small, light brown, and sunken; later they become dark and raised. When several spots are close together, the surface has a rough feeling to the touch, hence the name "sandpaper" melanose. Spots sometimes develop in a tear-streaked pattern [Picture ], resulting from infection caused by spores which wash down over the fruit surface during heavy dews or light rains. In other cases, large areas of the fruit surface crack in irregular patterns, resulting in the "mud cake" type of melanose.

---