Australian native forest trees and other
vegetation support a wide variety of animal species. Forest
mammals, birds, lizards, insects and other invertebrates feed
on all types of leaves, buds and flowers, wood and bark. Some
of these are predators of others. Under natural conditions,
the number of animals that feed and damage forest vegetation
are kept low by predators and environmental conditions. So
wide-scale forest damage rarely occurs.
Any animal that causes unwanted damage to trees
may be considered a pest. This damage may be extensive in
that it causes death or greatly reduces growth. Tolerance
to damage to pests will vary depending upon the goals for
planting, with greater tolerance in areas were trees are established
to revegetate wildlife habitat and less for those trees that
are planted with a high economic return in mind.
Plantations and farm forests, especially
during the establishment phase, may be more prone to damage
from local populations of plant-feeding animals. Plant-feeding
mammals can decimate newly planted or young seedlingsthe
leaves are young, nutritious and easily accessible. Some plant-feeding
insects also respond to the availability of nutritious food;
their numbers increasing rapidly while feed is available.
Insects can seriously affect the health of trees by quickly
consuming valuable leaf tissue and buds. This can kill the
seedlings or result in poor growth due to extensive leading
Newly planted seedlings are vulnerable to mammals and insects
for approximately three years. Ground-dwelling mammals become
less destructive as saplings develop sturdy trunks and leaves
grow beyond reach.
Extensive damage to trees is not always detrimental to their
growth rate or trunk development. If bud and leading shoot
damage is limited, significant leaf damage can be sustained,
especially on more mature trees. Generally, healthy trees,
and trees with rapid growth rates, are better able to withstand
damage from pests and diseases. Mature eucalypt trees completely
defoliated in one season might suffer no long-term damage,
especially if damage occurs late in the growing season.
Australian forests are also prone to diseases. It is common
to see eucalypt leaves covered with blemishes, spots or dead
patches. There are many causes. They include nutrient problems
and environmental factors such as nutrient deficiencies, drought,
waterlogging or frost. But one of the most common causes is
Fire is a regular part of the Australian landscape. Most of
Australias vegetation has developed ways to withstand
intense heat or to easily replenish itself after a fire. Unfortunately
fire can damage wood quality, encourage irregular tree growth
or lead to insect and fungal infections.
stock, vermin and wildlife
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