Ant's on my Fatsia Japonica
By Worzle
Berkshire,
United Kingdom 
I've learnt today that Fatsia Japonica produces a syrup substance called Honeydew which attracts ants. I've also learnt that this can cause a nasty black fungus but what I can't find out is how to control the Ants in a way that is not harmful to the plant. Any ideas?
10 May, 2009
Answers
honeydew is the waste of greenflies, it is then picked up as food by ants. ants will 'farm' aphids for the honeydew but as you have found out it causes a black sooty mould.
if you get rid of the greenfly you will find the ants go else where.
10 May, 2009
You can apparently use a pathogenic nematode, Steinernema feltiae which will help destroy the nest .
I have not tried this though so I don't have any feedback as to how well it works. I have normally had ants nests every year but never had any problem from them, so have never tried any method of control.
10 May, 2009