What are these infestations on a Silky Oak?

[Blackstump]

We have a Silky Oak tree up our driveway which was looking really good. Today my wife went for a walk and found all these infestations over almost the entire tree. Only a few branches have escaped, what are they and what is the treatment short of pulling it out and burning it. But that of course is an option. 
Thanks David. 

[Jason]

Welcome to the Bunnings Workshop community @Blackstump. It's good to have you join us. Please don't hesitate to post anytime you need assistance with a project around the house or garden. We have helpful members sharing advice and inspiration on the site every day.

Let me tag the wonderful @Noelle to see if she has experience with your Silky Oak trees and what the issue might be.

Jason

[Noelle]

Hi @Blackstump 

It's a bit hard to be definite but to me it looks like one or other of two possibilities:

1. Wasp nests

2. Bark boring larvae of some description that are causing gum/sap accumulations/nests

Unfortunately your photos are not clear or close enough to give a more positive diagnosis. Some close-up images would be helpful.

You could investigate with a long stick and try to scrape away one of the "deposits" to see what lies beneath. Maybe a long-sleeved shirt, mask and safety glasses should be worn, just in case you stir up a hornets' nest!

Either way, an insecticidal treatment of some sort would be beneficial. Start with something like an eco oil applied as directed, making sure to thoroughly wet each outbreak. I'm interested to hear and see further as to what you find.

[Blackstump]

@Noelle 

 

 

 This is the grub my wife found this morning digging around in a branch. 

[Noelle]

Hi again @Blackstump 

That's isn't good! These larvae are burrowing into the heartwood of branches, which will result in the death of the branch. The accumulations are most likely a mixture of sap and droppings.

Given this, I'd suggest cutting back all the affected branches into healthy, unaffected wood, and bagging the prunings so they can be put into the household garbage. Laying the bags out in the sun for a few days to kill the pests would be appropriate.

I can't identify the pest sorry, but its effect could be devastating if it has spread beyond this one tree. Unfortunately incidents like this can occur when the conditions are just right for a particular pest to breed. Keep a watch over other native shrubs nearby in case this is not an isolated occurrence.

[mich1972]

@Blackstump @Noelle  Definitely agree with Noelle, that doesn’t look good. I zoomed in on the photo and it looks like the grub burrows through the branch leaving a web with frass ( Poo ) sticking to it. Definitely cut and remove. It may help if you report it to your local Agricultural Department as they may be able to identify it. 

[Blackstump]

Thanks Noelle. Not good news. 

[Blackstump]

Thanks mich1972.