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Plague Locust Threat to Australian Agriculture
Brad Hinton
Economics, Commerce and Industrial Relations Group
3 October 2000
Introduction
Throughout this year the Australian Plague Locust Commission (APLC) (funded
by the Federal, NSW, Victorian, South Australian and Queensland Governments)
has issued bulletins warning of a potential plague locust disaster for
Australian agriculture this Spring.
These warnings have alerted farmers and government to the need to identify
and monitor risk areas in the months leading up to the locust hatching
season from September to November. Grain crops are particularly at risk.
The APLC predicts a major outbreak of plague locusts representing significant
threats to grain crops in large areas of NSW, South Australia and parts
of Victoria. Queensland is rated a moderate risk (see map over page).
The Agriculture Protection Board in Western Australia has identified and
been monitoring potentially massive outbreaks of locust activity from
Moora to Esperance.
Major locust outbreaks causing damage to crops were recorded in Western
Australia in 1990, in western NSW in 1992 and in parts of South Australia
in 1992, 1993 and 1997. This current locust threat is envisaged to be
considerably worse than these. Current crop damage estimates are difficult
to forecast but Agriculture WA says that potential damage in that state
alone could be up to $200 million without control measures.
The hatching season usually begins in September in warmer areas (northern
South Australia and north-western NSW) through to late October in cooler
areas (south-east NSW and Victoria). Egg hatchings in Western Australia
are expected to accelerate in early October.
Plague Locusts
The Australian plague locust (Chortoicetes terminifera) is one
of three major locust pests in Australia. The plague locust is the most
recurring and potentially damaging of the three. The other two are the
spur-throated locust (Austracis guttulosa) and the migratory locust
(Locusta migratoria). Locust outbreaks occur from time to time
across Australia depending on climatic factors.
Outbreaks of plague locusts often originate in semi-arid and arid zones
of Australia. During Summer 1999-2000 and Autumn 2000 these areas received
exceptional rainfall that allowed locust levels to build up to plague
proportions and provided ideal conditions for the laying of the eggs,
despite control measures.
Plague locust eggs laid in Autumn lie dormant in the resting stage through
Winter. Hatchings begin when moisture and temperature conditions are right
in the Spring.
It takes from 4 to 6 weeks for locust nymphs to reach fledging
stage and another 2 weeks to adult maturation enabling migratory flight.
The main danger to agriculture occurs where crops are still green. Crop
damage from bands of nymphs and migratory locusts can be significant.
Even crops approaching ripeness can be attacked, particularly in the small
green area below the grain head just prior to the readiness for harvesting.
During daytime, plague locusts may feed and migrate up to a distance
of 10-20 kilometres. At night they may fly hundreds of kilometres depending
on wind conditions. Predicting where and how far locust swarms will migrate
to is uncertain.
The Australian Plague Locust Commission (APLC)
The APLC was established in 1974 and became operational in 1976 to co-ordinate
the monitoring and control of plague locusts, including the spur-throated
and migratory locusts, considered a threat to interstate rural
industries, although the APLC may be invited to assist if requested. Western
Australia and Tasmania are not APLC members.
The APLC is funded and comprised of the Commonwealth Government (50%)
and the governments of NSW (32.5%), Victoria (10%), South Australia (5%)
and Queensland (2.5%).
The 1999-2000 budget allocation for APLC was $3.14 million.
The main functions of the APLC are preventative control using chemical
sprays, monitoring and forecasting in contributor states where interstate
migrations are likely to occur.
Preventative Control
Preventative control aims to control locust populations before they reach
outbreak levels and includes the monitoring, forecasting and treatment
of infested areas. The main control agent is a chemical insecticide, principally
fenitrothion. The optimum time to spray is about a fortnight after
hatching when locust nymphs aggregate into dense bands. Chemical
spraying that targets adult locusts in aerial swarms may occur at a later
stage depending on location and environmental limitations. Locust bands
and swarms in pastoral areas are easier to aerial spray because of reduced
limitations.
APLC research in conjunction with the CSIRO has looked at biological
locust control using a naturally occurring fungus that will be tested
this season in some sensitive areas.
Monitoring and Forecasting
Monitoring is by ground surveys in Eastern Australia and by reporting
of locust activity by farmers and agricultural field officers. Long distance
migrations are recorded by eight light traps in Eastern Australia. The
light traps attract locust numbers and estimates are made on the size
of the swarms. The light traps are located in Oodnadatta and Dulkannina
in South Australia, at Fowlers Gap and White Cliffs in NSW, and at Nooyeah
Downs, Birdsville, Julia Creek, and Longreach in Queensland.
Forecasting possible locust plague locations and monitoring developments
are important for preventative control. Locust surveys and reports, meteorological
data and quantitative modelling are used by APLC in a computerised Decision
Support System.
Current Control Activities
Landholders are largely responsible for locust control on their own properties
using ground control equipment. Local councils and farmer groups often
work together to organise some control measures.
The APLC will target high-risk areas for aerial spraying of plague locusts
across member states to limit potential interstate migrations.
Government Responses
The Federal Government provides half the total funding for the Australian
Plague Locust Commission within the Department of Agriculture, Fisheries
and Forestry. Commonwealth funding for 1999-2000 was $1.6 million.
The NSW Department of Agriculture and the Rural Lands Protection Board
assist in plague locust control. Chemicals have been made available to
farmers and financed from levies to the Noxious Insect Destruction Account.
Aerial spraying by APLC and landholders has already begun in western NSW.
Queensland's Department of Natural Resources is monitoring the south-west
of the state where a moderate risk has been forecast.
North-west Victoria is a high risk area. The Victorian Government pledged
an additional $1 million on September 13 to fund aerial spraying. The
risk of locust migrations from NSW and South Australia is a significant
danger.
The South Australian Government has allocated $6 million for the 2000
Locust Control Program. In addition, local councils will be reimbursed
up to 95% from the South Australian Local Government Disaster Fund to
help defray locust control costs. In August the State Government announced
a $1 per hectare rebate scheme for farmers using approved and certified
chemicals for locust control.
Agriculture WA has a Locust Response Plan and, with farmers, is gearing
up for a $30 million campaign over 2 million hectares.
Conclusion
A significant threat to crop production exists from plague locusts in
the coming months although chemical spraying and crop maturity may mitigate
disaster.
(Map used with permission from APLC from their website at: http://www.affa.gov.au/aplc
)
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