Hello
can anyone identify what this area (plm 30 cm) with densely spread orange spots (fungus?) on sections of the trunk are, and what to do about them? 

This has killed 2 Acer palmatums already, starting high up in the trunk and descending fastly, with all branches above the affected area dying. 

The pictured trunk was infected for the top 30 cm and cut off 30 cm below the lowest margin of the diseased section, far into the healthy-looking trunk. Nevertheless this infection has spread to below the cut, so it seems to have spread downward in the healthy-looking trunk prior to cutting it.

It is planted in the garden in the Netherlands, temperate climate, has been very wet this year.
 

I have not seen it myself before. But I googled and found a common funkar infection that gives that symptoms. Coral spot desease. Nectria canker.

many thanks!