Home' Grower : July 2010 Contents The South Australian Grower -- July 2010 7
Avocado growers on red alert
THE nation's avocado grow-
ers have been asked to keep
a close lookout for a foreign
strain of thrips that could cause
significant losses if they arrive in
Scirtothrips perseae was discov-
ered damaging avocado fruit and
leaves in California in 1996. It is
native to Mexico
For chief executive officer of
Avocados Australia Antony
Allen, keeping pests such as avo-
cado thrips out is a high priority.
"The introduction of a pest like
this would be a disaster to the
Australian industry," he said.
"The feeding by adults and lar-
vae causes serious distortion to
young leaves, and extensive
'corky' damage to the surface of
young avocado fruit."
The industr y is on the front
foot in managing the risks posed
by exotic pests
In southern California, the
thrips build to high densities on
immature avocado foliage and
fruit in late winter and spring.
The cumulative feeding damage
by lar vae and adults can induce
premature tree defoliation.
The brown scarring and dam-
aged fruit is either unmarketable
or gets downgraded in packing
Mr Allen said an outbreak of
avocado thrips would have a
substantial impact on affected
growers through production
losses and reduced fruit quality.
There was no guarantee the
thrips could be eradicated once
A response to avocado thrips
would cost industry and the
community a great deal.
Ongoing control costs would be
The best approach to dealing
with the threat would be to:
• Take every precaution when
introducing new plant materi-
al onto orchards.
• Maintaining a lookout for the
thrips and any of the telltale
signs of its presence on trees.
• Reporting immediately any
suspicions to the Exotic Plant
Pest Hotline on 1800 084 881.
Biological control of avocado
thrips has been attempted, but
the rate of breeding of this pest
usually outstrips that of any pred-
ators and traditional biological
control is not considered a viable
option in commercial orchards.
Avocados Australia has been on
the front foot in managing the
risks posed by exotic pests. Since
2007, there has been a national
Avocado Industry Biosecurity
Plan in place. It is being
reviewed and updated with Plant
Health Australia, and an
Avocado Orchard Biosecurity
Manual is scheduled to be
released next year.
"Maintenance of our plant
health status is vital for retaining
existing trade, negotiating access
to new overseas markets and
ensuring the future profitability
and sustainability of the
Australian avocado industry",
Mr Allen said.
General Manager Programs for
Plant Health Australia Rodney
Turner says the thrips were pre-
Foreign strain of thrips could induce premature tree defoliation
damaging fruit and leaves
Produce either unmar-
ketable or downgraded
Biological control not a
AT A GLANCE
Brown scarring on damaged avocado fruit from the thrip could cost the industry in
Australia millions of dollars.
sumably introduced inadvertently
into California, most likely on young
seedlings, and they now infest about
95 per cent of farms in that state.
"However, Avocado thrips have
not, as yet, been dispersed more
widely, despite a worldwide trade in
avocado fruit," he said.
"For its numbers to build up, the
thrips appear to be fully dependent
on the young growing tissues of the
Details: www.farmbiosecurity.com.au or
EPPH 1800 084 881.
Spotting avocado thrips is difficult
enough. Because of its small body size
-- about 2mm long -- and the
undistinguished yellow colour,
satisfactory recognition of an adult as a
member of the genus Scirtothrips really
needs expert examination under a
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