Many years ago, I managed to get rid of a pretty hefty sawfly larva
infestation from a Dwarf Sugar Gum (E. cladocalyx nana) with a systemic
insecticide called 'Metasystox'. I don't know whether it's still
available (or, indeed, whether it's regarded to be an ethical and
environmentally safe alternative), but you could ask at a nursery or
your local forestry office?

The Metasystox came as a tin of granules, which I sprinkled round the
base of the tree and watered in. The idea is that when the sawflies suck
it up from the plant's tissues, they succumb! It took about a week to
see the rotten little horrors plummetting to their demise ('SPLAT!!! -
Bwahahahahahahah!'), but it worked and the larvae have never bothered
the tree again. Which is good, because it's host to my collection of
orchids, a PeeWee's little mud-nest and zillions of birds that come to
visit the garden!

It has occurred to me that a systemic poison could indeed kill other
*good* sap-sucking creatures on a tree and perhaps even a bird which
might eat them. This is the part you'd really need to be clear about
before you decided to try it.

Speaking of birds' nests, I was helping my Mum by watering her
shade-house the other day when she grabhbed me as if she'd suddenly gone
mad and snatched away the hose! There, snugly hidden in the depths of a
large hanging Boston fern, was a Collared Turtledove sitting on two
eggs! I *know* I should've shushed it off and destroyed the nest... but
I couldn't! I tiptoed away and thought 'How lovely!'

--
Trish {|:-}
Newcastle, NSW, Australia