Buckthorn Blight

As mentioned in previous posts, our woodlot is infested from corner to corner by the two common invasive species of Buckthorn. These are the Common buckthorn [Rhamnus cathartica] and the Glossy buckthorn [Frangula alnus]. Both have also been referred to as European buckthorn in different sources, so I have decided to avoid that name altogether.

In the last week I have found a disease on both species of buckthorn that in some cases has completely defoliated the bush. The disease is quite widespread but still only infecting selective trees. It looks like a bright orange mould as pictured here.

I wonder what that is?