black stuff on citrus tree

[chipster2]

Looks like mold on leaves and limbs. What do I use to get it off and keep it from coming back?

[Thunderbird+]

The black mould is its self relativly harmless and it should be possible to remove with a hose with a high pressure nozzle.

The cause of the problem is likely to be sap-sucking insects ie aphids or white fly that feed on the under sides of leaves and exude a clear sticky substance known as honey dew, this falls onto the surfice of leaves below and creates the conditions for the black mould to grow, therefore the best form of defence is to attack the greenfly/aphids with a suitable insecticide following instructions on the labell for indoor or outdoor use. Good Luck.