The New Zealand Plant Conservation Network

My ten year old pukanui is being attacked by some creature eating the bark away below the leaf clusters at the end of the branches. The leaves are falling off.

This sounds more like an attack of the water borne oomycete Phytophthora (a water mould). If the leaves have suddenly started falling off, and the bark is falling away this is quite typical of this disease, and I am sorry but there is nothing you can turn to save your tree. I suggest you cut it out and try and remove the stump, and don't plant any Meryta in that area again. This disease is common in Auckland (it killed all of my trees in 1998)

This sounds like an attack of the oomycete (water mould) Phytophthora. It causes the bark to rupture and bleed, and shed, and the leaves to (often quite suddenly) fall off. You cannot fix the problem. Its best you remove the tree and try and dig out the stump. Don't plant any phytophthora sensitive species back in that spot. Alas this disease is common in Auckland. It killed all of my plants in 1998.