It certainly looks like sooty mold. Sooty mold is a dark fungal growth that can be found on leaves and twigs especially when trees are infested by honeydew excreting insects such as aphids, mealybugs and whiteflies. The mold grows on the insects excretions. You need to control it by a regular spray program. If you would rather not spray with a poisonous spray, then use a good horticultural oil spray, which is non toxic and works VERY well.
