western-queensland-gardening-guide.pdf - South West NRM

Chapter 7. Insects affecting farm trees
Farm trees are under threat from a variety of insects which can result in the
premature death and rapid deterioration of young regrowth and mature trees.
Insects attack all stages of growth. Trees seldom, if ever, die following a single bout
of insect damage. Repeated defoliation over a number of seasons or years is more
likely to kill trees. Few native trees escape insect attack, but not all insects found on
trees cause damage. The insects directly affecting trees are divided into four
categories, depending on their mode of feeding:
leaf-eating
sap-sucking
wood or bark feeders
gall formers
White cedar moth (or hairy grub)
This pest is very common in western Queensland and the larvae may completely
defoliate trees, usually during the period from January to March.
The moth lays its eggs on the bark and foliage. The brown, hairy larvae are 2.5 cm
(1 inch) to 4 cm (1% inches) long, and feed during the night sheltering near the base of
the tree during the day. Jn the evening they may be seen, in large numbers, moving up
the trunk of the tree. en fully grown they find a sheltered place under bark or in
crevices of posts or buildings and construct their pupal cocoons.
completely defoliated, the 1 will leave it and can often be seen moving in
procession to another tree. e cedar appears to be the only host of this pest.
Contact with the hairs on the grubs causes skin irritation to some people.
Control
The larvae may be trapped in a folded bag, placed around the tru'nk of the tree, and
then destroyed. Alternatively a maldison (Malathion) foliage spray may be used, or the
grubs may be sprayed where they shelter on the ground during the day, or when they
are moving up the trunk in the evening.
Wood borers
There are a number of different species of borers, but the damage caused by each is
similar and is treated in the same way. The injury to the tree usually occurs near a
branch fork, or where the bark is cracked or has been broken. The hole made by the
borer in the tree is usually surrounded by wood dust and sap from the tree and weblike
fibres left by the borers.
Control
Prevent infestation by maintaining the good health of the tree. Prune and burn
infested twigs and small branches. Where the borer holes occur in large branches or in
the trunk, trim around the damaged area to properly expose the hole, but do not
extend the damaged area during the trimming. Then, brush the area clean and insert
flexible copper wire into the hole twisting it to kill any larvae which are present. Using