Anthracnose(?) in London Planes

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Over the last two years I have seen two Platanus x acerifolia that have been affected by a leaf spot disease identified by a plant pathologist as - Discular umbrinella.
In both cases the trees had been stressed/predisposed by 1. intentional (but poorly carried out) poisoning and 2.accidental poisoning (a "weed and feed" solution containing dicamba).

In both cases the symptoms are very much like anthracnose and appeared in Spring. In case 1. the tree survived. In case 2. it is in a severe state of decline with the disease reappearing during the following Sping. For both trees measures were taken to improve growing conditions eg mulch, judicious use of slow release fertiliser, judicious irrigation over summer etc.

Questions:

a. Is this disease the same as what is called in the US - Dogwood Anthracnose?
b. Does it attack Planes over there?
c. Appart from the recommended treatments for Sycamore Anthracnose (Gnomonia veneta) are there any other effective treatments eg. are there any useful fungicide implants (I assume the answer is no and I cringe to ask given the possible side effects for a sick tree - but thought I should ask anyway)

Any comments / advise would be appreciated and a North American perspective valued for what tends to be unusual problem here.

Thanks in advance,

Garry Clubley
Consulting Arborist
Sydney
Australia