Another Insect Question

Hi all


I have another issue/question on pests. Regarding my last post, I will provide an update on the issue with the galls when I get some final results from my trials.


My new pests are actually killing my trees -Tuckeroos this time. And only the Tuckeroos.


Have a look at the attached pics. Something is cutting neat rings around the branches, which is slowly killing the tree.


I have done the usual on-line searches, but can find nothing.


Does anyone have a suggestion about what causes this damage and how I can prevent the damage. I have tried some of the sprays like pyrethrum and white oil, but seemingly with no effect. I have looked over the trees very very carefully and can find no insect or grub that seems out of place or near the scene of the crime.


I have the Tuckeroos growing near other natives, but this is not happening to any other tree. So far, whatever is doing this, is attacking younger trees. The more mature trees, say over 3 or 4 years, appear to be unaffected.


Thanks
darrell