I had two tridents inflicted with these exact symtoms in 2015.
I read the threads here diagnosing as thrips in the newly opening buds, and got hold of some Rogor, and proceeded to treat heavily in 2016 in the hope of nuking the thrips. The results of this treatment were nothing but disappointment - no change. And the health of the trees was deteriorating quickly - tertiary branches will start to blacken and die back as the new buds continually fail, leaving the tree exhausted for energy.
Read a bit more, I thought it could be a fungal disease, so for 2016 I got hold of Daconil, and treated from the end of winter through bud-break into late spring - but again, no joy.
Feeling beaten, I nearly binned both trees, but desperation lead me to research more widely for the 2017 season, and I came to the conclusion it was a fungal disease called anthracnose. From my copious amounts of reading, if a tree is suffering this disease, once inflicted the chances of recovery are 50/50.
Not to give up, for 2017 I lightly repotted both trees into an almost inorganic mix of pumice and lava rock, lightened the watering regime to keep the roots on the drier side, and treated heavily with thiophanate-methyl (Cleary's 3666).
The results have been good - one tree is on it's way to full recovery with healthy growth, no sign of leaf deformation or bud die-off, and the darkened tertiary branch colour is starting to recover the normal trident bark colour.
The other, which has suffered a bit worse over the last 2 years, has not recovered as well, and is still struggling..... but I will persist with this treatment into next season before giving up.
I think it is a fungal disease infliction (anthracnose) as result of over-watering and keeping the roots too damp.
From my experience, I am convinced it's not thrips.
Also from experience, you can get your hands on Rogor, Daconil, and Cleary's 3666 in Australia ...... you just have to know where to look.
