Peltoschema orphana is the most common leaf beetle found on Acacia, usually silver wattle. Commonly called the fireblight beetle it can cause devastation to silver wattle populations and even kill trees by defoliation. This versatile little beast is polyphagus and was feeding, with several others, and their larvae, on Eucalyptus which is uncommon but has been recorded before.
On A. mearnsii. Many plants in the area dead or defoliated. Many still healthy too. In this this area A. leprosa var. uninervia is also being seriously damaged or killed (apparently by a very similar but different species).
On Acacia mearnsii - plant only defoliated a small amount but mearnsii all but disappeared from this location a couple of years ago. A few new plants returned last year and this year. On the volcanic plains.