Agriculture Reference
In-Depth Information
tumefaciens
. The trunks and other woody parts of infected vines have growths or
galls at the site of infection. Pierce's disease (
Xylella fastidiosa
) is another bacterial
disease worthy of mention, since it is not present in Australia but widespread in the
USA. The disease is spread by various insect vectors and there is concern that this
disease may be introduced into Australia in the future.
There are a number of viruses that will also attack grapevines; generally they
result in distorted and discoloured leaves. The most common one is Grapevine Leaf
Roll Virus (GLRV). There are five types, types 3 and 5 are the most prevalent in
Australia. Typing is based upon the outer structure (protein coat) of the virus. The
leaves of vines infected with GLRV have a bronzed appearance which may just be
present around the edge of the leaf and generally does not extend the veined area.
This leaf discolouration only occurs in the autumn; throughout the spring and sum-
mer leaves appear unaffected. Essentially leaves appear to senesce prematurely.
GLRV reduces yields and can delay fruit maturity.
Pests
Light Brown Apple Moth
This moth attacks a wide range of fruit crops, damage to grapevines is caused by the
larvae which feed on shoots and developing bunches. Larvae feeding on bunches
facilitates bunch rot diseases, primarily
Botrytis cinerea
or grey mould (see above).
The insect tends to feed on protected locations, e.g. with a compact bunch, which as
discussed previously, will be more susceptible to fungal attack.
Phylloxera
Phylloxera or
Daktulosphaira vitifolii
is a very destructive pest of grapevines,
which nearly led to the collapse of grape growing in Europe after its introduction
from North America. Phylloxera is an aphid that feeds on the roots of the grapevine.
Despite the fact that this insect has been present in Australia since 1877, it is still
confined to a relatively small number of viticulture regions. This has largely been
due to quarantine practices that limit the movement of vine material between re-
gions and also good vineyard hygiene.
Nematodes
Nematodes are microscopic worm-like organisms that live in the soil and are some-
times referred to as eel worms. Many nematodes are saprophytes, feeding on dead
tissue in the soil, while others feed on soil bacteria and even on other nematodes. A
small minority of nematodes are parasitic for plant roots. There are three types that
