It looks like I'll be replacing my Sydney Golden Wattle a bit sooner than I expected. It doesn't look unhealthy, does it?
We had some close friends over for lunch on Friday and one of them mentioned something flowering yellow up the back. "But I don't have anything yellow there!" and off I went to have a look. Unfortunately, borers have attacked the wattle. I cut off some yellowed branches the next day.
The froth here is sap; the tree is trying to defend itself by drowning the borers. Unfortunately, this tree is weeping froth everywhere. The sweet sap has attracted flies, too. If I were to cut off all the infested sections, there would be nothing left but a stump. Borers go for stressed or weak trees, so this wattle's days are numbered. I'll remove it in autumn, when its shade is no longer useful.
Borer damage results in the bark dying and falling off in patches, exposing the wood (really bad attacks can ringbark the tree). The "eye" is a borer entry hole.
Close-up of the borer hole, showing the tell-tale sawdust around it. Some people say you can poke wire up the hole to kill the borer, but as the borers are just telling you the tree is in trouble, I think it's a pointless exercise.
On the bright side, it means that I'm just a bit closer to buying an Acacia pycnantha...