It is a fungus, so theoretically any fungicide should deal with it. Damp airless conditions tend to help it develop, so getting good airflow round plants does help......a little.
Have a look at Ideas Genie
Very good personal help available from the designer too.
The Rowan is one called Pink Pagoda. Though I think the one in the pictures may well be a self seeded one from the original. We also have white, red, yellow and copper coloured berried forms too.
Take a September stroll with me.
The first picture is of Gemma. I found her abandoned down our lane when she was about 5 weeks old.
Cannot get a Link to appear, back in a moment.
Sow fresh, leave outside over winter. Watch out for mice who love to eat them.
OR,Soak in warm water overnight, then put the wet seeds in the Salad section of the fridge for 3 months, then sow as for normal seeds.
Did you remove the compost in which the trees came and spread the roots out? Not doing that is the major cause of trees not growing properly. The roots seem to prefer the compost in which they were potted and instead of spreading out, they just go round and round, then when the food in the compost runs out, they fail.
And some Dahlias
A few flowers from Bodnant and Dorothy Clive
If it is Echinops, then where are the bracts which should be just below the flower?