There are two forms of fungicide that can be used.
The first is a blanket type application:
The plant is drenched from top to toe with the fungicide. This application works on contact or smothering effect. Normally a couple of applications will control the problem.
The role of this fungicide is more of a preventative nature. So normally in periods of very high humidity or at times when fungus attacks are more prevalent, a quick drenching of this form should keep your fungus problems under control.Here at the Laurels we use Mancozeb (see disclaimer) . The active ingredient in Mancozeb is Mancozeb.
There are numerous fungicides available through the Retail Nursery and Produce Store outlets. Some of these combine two different chemical to do a better job. Have a talk with your local nursery to see what is available.
Remember: Try to use the least harmful (especially to yourself)! Always read the instructions fully and apply as per the method so indicated.
All ways protect yourself: wear suitable rubber gloves, cover-
Sometimes when more serious fungal problems persist a Systemic type of fungicide is required.
These fungicides work from within the tree. The tree absorbs the active ingredient in the spray through its leaves. So do not drench the tree as before, you will be wasting the spray.
At the Laurels we use Fosjec400 (see disclaimer). The active ingredient in Fosjec is Phosphoric Acid. (once again there are numerous systemic sprays on the market, so consult your local nursery or gardening expert for more info on what you should use).