Locust Bulletin April 2016

​​​​​​​​​​​​​ISSN 2204-9851

The Locust Bulletin is produced each month during the spring—autumn period and includes a general summary for each major locust species, details of known distributions with regional forecast and maps of locust distributions.

Table of Contents



General situation in March and outlook to spring 2016

Australian Plague Locust
Spur–throated Locust
Migratory Locust

Australian plague locust
Chortoicetes terminifera

Migration activity has redistributed current locust populations, contributing to noticeable increases in parts of New South Wales, South Australia and northern Victoria. Breeding in Southwest Queensland and the Far North region of South Australia in January produced localised high density nymphs that fledged during the second half of February. Subsequent migrations brought adults into Far West and Far Southwest New South Wales, and the Northeast region of South Australia, but no swarm formation has been identified. Further movements in mid-March within New South Wales resulted in a population increase in the Riverina and small immigrations into northern Victoria. Surveys identified a widespread medium density population in western regions of New South Wales, however redistributions resulted in subsequent declines in numbers in some areas. Heavy rainfall in northern regions of South Australia, and in Southwest and Northwest Queensland during March produced favourable habitat conditions for locust survival and possible breeding.

In New South Wales, consistent medium density adults were identified in the Broken Hill area in early March after reports from landholders. Surveys in mid-March recorded medium density adults throughout the Broken Hill, White Cliffs and Wilcannia districts of the Far West region, the Ivanhoe, Wentworth and Balranald districts in the Far Southwest and the Hay, Moulamein and Hillston districts of the northern Riverina. Samples showed some females were developing eggs. Adult densities were generally lower in the Central West and eastern Riverina, but numbers increased in the Deniliquin area on 18 March after the passage of a low pressure weather system.

Population density remained generally low in the Central West and Central Highlands regions of Queensland during March. Surveys identified low density adults and occasional nymphs in the Blackall, Tambo, Barcaldine and Springsure districts, and in the Charleville–Roma area of South Central Queensland. In late March, medium density adults were recorded in Quilpie and Bulloo Shires of the Southwest region.

There were several periods of migration in South Australia during March. Locusts were reported from Port Augusta, Innamincka, Dulkaninna and the Hawker–Parachilna area. Surveys in mid-March identified low density adults in the Southern Flinders Ranges, Jamestown–Burra and Morgan–Renmark areas, and in late March medium density adults were recorded around the Northern Flinders Ranges and parts of the Far North region.

There were several small immigrations to North Central Victoria from adjacent areas of New South Wales. Low density adults were reported near Kerang and Echuca on 10 March and medium density adults near Mitiamo on 22 March. These events coincided with the passage of low pressure weather systems. Surveys in the Echuca–Swan Hill and the northern Mallee district in mid-March identified only low density adults.

The outlook for autumn is for medium density adults to persist in the Far Southwest, Riverina and Central West regions of New South Wales, parts of the Far North and Northeast regions of South Australia, and in limited areas of North Central Victoria. Protracted low–medium density egg laying is likely during April and May. While significant swarm formation is unlikely, some localised aggregation and swarm egg laying is possible. Most eggs laid in these regions after mid-March will enter diapause dormancy. Further breeding was possible in parts of the Southwest and Northwest Queensland, and the Northwest and Far North regions of South Australia, after heavy rainfall in mid-March, but the probability of late autumn southward migrations remains low. There is a low risk of widespread infestations affecting agricultural regions across several states during the remainder of autumn or in spring 2016.

5 April 2016

Spur-throated locust
Austracris guttulosa

Adult population levels increased markedly in Northwest and Central West Queensland during March with the fledging of nymphs from summer breeding. There were still widespread nymphs at various development stages in these regions during March, which indicates that breeding continued in February and a further increase in adult numbers will occur during April. Surveys in mid-March identified Scattered–Numerous density adults and Present density nymphs at various life stages in many areas of Longreach, Blackall-Tambo and Barcaldine Regional Council (RC) areas. Present–Numerous density nymphs were recorded at most transect locations in the Longreach area. Scattered–Numerous density adults and occasional Present density nymphs were also recorded in the Springsure–Rolleston area of the Central Highlands and the Morven–Roma area of South Central Queensland. In late March, Numerous–Concentration density young adults and Present–Numerous mid- and late instar nymphs were identified at many locations in the Muttaburra–Hughenden, Winton–Kynuna and Julia Creek–Richmond areas. Several large swarms of young adults were recorded in these areas. This represents a significant population increase over the levels recorded in February. Similar population increases are likely to have occurred in the northern Central Highlands, Southwest and Queensland Gulf regions, and in adjacent regions of the Northern Territory, where habitat conditions have been favourable for breeding. Larger populations are likely to be in the northern regions. Very few adults and no nymphs were recorded in northern New South Wales and northern South Australia.

The continued presence of nymphs at various development stages, including younger instars, in Central West and Northwest Queensland during March indicates egg laying continued during January and February. Favourable habitat conditions for nymph survival have been maintained by heavy rains during the first half of March in some areas. Egg development to hatching in this species takes 3-4 weeks and nymph development 8-10 weeks. Females can lay multiple times during summer.

Nymphs of this species usually do not aggregate to form bands, but can reach densities of 30 m2 in locally favourable habitats. Nymph numbers are likely to have peaked during March, but residual late instars will be present during April. Fledging will continue during April and May. Any egg laying in northern New South Wales or South Australia is likely to have produced only occasional low density nymphs.

The outlook is for an overall increase in the young adult population during autumn to an equivalent or higher level than in 2015. There is a moderate risk of further swarm formation during late autumn 2016, particularly in the Central West, Northwest and Central Highlands regions of Queensland. Migrations of young adults can occur during autumn and swarms often over-winter in forest areas and riparian tree lines during winter. There is a moderate risk of some swarms migrating to cropping areas in Queensland in late spring 2016.

Migratory locust
Locusta migratoria

Surveys in Queensland during March identified low density adults and occasional nymphs in parts of the Central Highlands and northern South Central regions of Queensland. Isolated–Scattered density adults were recorded in Springsure–Buckland, Rolleston–Arcadia and Mitchell–Injune areas. Present density mid-instar nymphs were detected in the Arcadia Valley. Rainfall in these areas during the March will maintain suitable habitats for continued low density breeding, but may limit the development of gregarious populations. This species is capable of continuous breeding during summer and autumn, resulting in populations comprising multiple life stages.

There is a moderate probability of small gregarious populations developing in parts of the Central Highlands or eastern Central West regions of Queensland during autumn. Gregarisation can occur at local scales and is often associated with cropping. However, the absence of any identified high densities at this stage of the season indicates a low probability of a widespread infestation developing during autumn or winter 2016.

It is important that any locust activity be reported as soon as possible to your local biosecurity authority, primary industries department or to the commission. A toll–free call to the APLC can be made on 1800 635 962. An answering machine is attached for after–hours calls. Reports can also be e–mailed to APLC or made through the internet at Australian Plague Locust Commission.

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Australian plague locust distribution 1 March to 1 April 2016

Map of Australian plague locust distribution - March 2016

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Spur-throated locust distribution February-March 2016

'Map of spur-throated locust distribution - February-March 2016

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Situation in March and forecast to spring 2016

New South Wales

Central West and Northwest Plains

Central West, Northwest and Central Tablelands Local Land Services

Locusts and conditions

  • The locust population remained at generally low densities in surveyed areas of these regions.
  • Surveys of the southern Central West LLS area in mid-March identified Isolated–Scattered density adults and occasional late instar nymphs in the Nyngan–Tottenham–Tullamore areas. Scattered–Numerous density adults were recorded in the Condobolin–Euabalong–Tullibigeal area.
  • There was patchy light–moderate rainfall (<20-40 mm) in parts of the Central West and Central Tablelands LLS areas during the second and third weeks of March.

Forecast

  • Populations are likely to remain at generally low densities in most areas during autumn and swarm formation is unlikely to occur.
  • There is likely to have been some low–medium density egg laying in late March, which will continue during April and May. The majority of any eggs laid after mid-March will enter diapause and not hatch until early spring. The known autumn distribution indicates that some nymphs, most likely at low–medium densities, are likely to develop in the southern Central West LLS area from late September.
  • There is a low probability of significant immigration from other regions during April or May.

Risks

  • There is a low risk of widespread infestations developing during the remainder of autumn or in spring.

Riverina

Riverina and Murray Local Land Services

Locusts and conditions

  • Redistributions and migration from the Far West and Far Southwest regions during March contributed to a moderate increase in population level in the Riverina. Winds associated with the passage of low pressure weather systems during 6–8 and 17 March are likely to have resulted in population movements and were followed by reports of locusts.
  • Surveys in mid-March identified a Scattered–Numerous density adult population in the western Riverina Local Land Services (LLS) area. Isolated–Scattered density adults were identified in the Narrandera and Jerilderie districts. No nymphs were detected.
  • Locusts were reported to have appeared in areas southwest of Deniliquin on 18 March. Numerous–Concentration density adults were subsequently identified along roadsides in the Womboota area.
  • There was light–moderate rainfall (<20­–40 mm) in Murray and eastern Riverina LLS areas during 15-21 March.

Forecast

  • Although adult population increased during March, this is unlikely to result in the formation of swarms, other than possibly in restricted locations. Habitat conditions remain unsuitable for egg laying in most areas, although autumn egg laying is often not limited to areas of recent rainfall.
  • Adults are likely to persist in low-medium densities throughout the remainder of autumn, with the likelihood of localised but protracted egg laying. Most egg laying is likely to be at low density, but could be concentrated in areas adjacent to irrigated pasture or crops.
  • The majority of any eggs laid during March or April will enter diapause and not commence hatching until late September. There is a moderate probability of localised medium density nymphs developing in parts of the Riverina in October, and small Bands possible in some locations.
  • There is a low probability of significant immigration from other regions during April or May.

Risks

  • There is a low risk of a regional infestation developing during autumn or spring.

Far West and Far Southwest

Western Local Land Services

Locusts and conditions

  • Redistributions and immigration contributed to changes in population level during March. Population densities increased in the Broken Hill area in early March, and by mid-March there was a widespread medium density adult population in the southern Far West and throughout the Far Southwest regions.
  • Landholders near Broken Hill reported on 7 March that there had been an increase in locust numbers on their properties. Surveys identified consistent Numerous density adults along roadsides on the western side of the Barrier Range and between Broken Hill and Menindee. The distribution information indicates immigration to the Broken Hill area at the start of March, probably with some interstate component, and subsequent redistribution to the south and east.
  • Surveys in mid-March identified a widespread Scattered-Numerous density adult population in the Broken Hill, Packsaddle, White Cliffs, Wilcannia, Menindee, Ivanhoe and Darling Anabranch areas. However, adult numbers had declined in the Broken Hill–Menindee area.
  • Only Isolated–Scattered density adults were identified in the Broken Hill, White Cliffs and Tibooburra districts in late March.
  • The Fowlers Gap and White Cliffs light traps recorded low numbers of locusts during 3-12 March, with 50 caught at Fowlers Gap on 4 March and 50 at White Cliffs on 7 March.
  • There was light–moderate rainfall (<20-40 mm) in the Broken Hill, Cobar and Wilcannia districts during 8–16 March, and light falls in the White Cliffs district in the last week of the month. Vegetation became mostly dry during the second half of the month.

Forecast

  • Habitat conditions were unsuitable in most areas for rapid egg development or laying during the first half of March. Rainfall in mid-March may have initiated some sporadic medium density egg laying in late March in the Broken Hill–Menindee area, but is likely to result in localised nymphs and possibly some Bands developing in spring.
  • Some adults are likely to persist at medium densities in the Far Southwest region during April and May, and further sporadic egg laying is possible in some areas.
  • The majority of any eggs laid from late March in the Far West region, and from mid-March in the Far Southwest, will enter diapause and not hatch until early spring.
  • There is a low probability of any significant immigration from other regions during April or May.

Risks

  • There is a low risk of a widespread regional infestation developing during autumn or spring.

All locust activity should be reported to your Local Land Services or the Department of Primary Industries, NSW. A toll-free call to the APLC can be made on 1800 635 962. An answering machine is attached for after-hours calls. Reports can also be e–mailed to APLC or sent through the web page at Australian Plague Locust Commission.

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Queensland

Southwest

Barcoo, Bulloo, Quilpie and Diamantina Shire

Locusts and conditions

  • A medium density adult population was identified in Bulloo and Quilpie Shires at the start of April.
  • Heavy rains and flooding prevented survey of the region until the end of March. Scattered–Numerous density adults were identified in the Thargomindah–Durham Downs–Nappa Merrie and Quilpie–Eromanga–Mt Howitt areas of Bulloo and Quilpie Shire. No nymphs were detected during surveys.
  • The Nooyeah Downs light trap recorded low numbers of locusts during the second half of March.
  • Habitat conditions remained favourable for nymph survival in most areas, and for further breeding in the Windorah–Mt Howitt area during February, but became dry in many areas by the end of the month. Surveys detected no nymphs, suggesting no widespread high density egg laying occurred in February.
  • There was moderate–heavy rainfall (20->40 mm) in parts of Bulloo, Barcoo, Quilpie and Diamantina Shires during 8–16 March, and further light–moderate falls in Bulloo Shire during 16–23 March. Vegetation remains green in habitat areas that received heavy rainfall in February and March.

Forecast

  • Heavy rainfall in Diamantina and Barcoo Shires in March produced favourable habitat for further breeding in mid-March. If the detected adult population level in other Shires extended to those areas, localised medium–high density nymphs could develop during April. This would result in an increase in adult numbers late in the month, but at this stage there is a moderate probability of adult activity extending into May or June.
  • Adults are likely to persist at medium densities during April and sporadic egg laying could occur in parts of southern Barcoo or Diamantina Shire. The majority eggs laid at that time will enter diapause and hatch in early spring.
  • There is a moderate probability of continuing migratory redistribution within the region during autumn.

Risks

  • There is a low risk of a widespread regional infestation in autumn or spring.

Central West & Northwest

Longreach, Barcaldine and Blackall-Tambo Regional Council. Boulia, Cloncurry, Flinders, Mckinlay, Mt Isa, Richmond and Winton Shire

Locusts and conditions

  • The locust population level remained generally low in surveyed areas during March.
  • Surveys of Longreach, Barcaldine and Blackall-Tambo Regional Council (RC) areas in mid-March identified Isolated–Scattered density adults in most areas, with Present density late instar nymphs at a single location north of Barcaldine.
  • Surveys in Winton, McKinlay, Richmond and Flinders Shires in late March identified only occasional Isolated density adults.
  • The Longreach light trap recorded low numbers of locusts on several days in mid-March.
  • There was moderate–heavy storm rainfall (20->40 mm) in the Northwest and northern Central West regions during the first and second weeks of March. There were light–moderate falls in eastern Barcaldine and Blackall-Tambo Regional Council (RC) areas during the last week of March. Locust habitat became mostly dry during March, apart from localised areas near Bimerah, Winton and Hughenden that received heavy rainfall.

Forecast

  • Despite favourable habitat conditions in the eastern districts of the Central West and in Winton Shire during February, very few nymphs and no increase in adult population was detected in March. Some egg laying was possible in localised green habitat areas in the second half of March, which would produce nymphs during April. At this late stage of the locust season, the probability of a significant population of nymphs developing in April and of a subsequent large increase in adult densities in May remains low.
  • There is a low probability of significant immigration from other regions during April or May.

Risks

  • There is a low risk of a widespread regional infestation during autumn or spring.

Central Highlands

Central Highlands and Isaac Regional Council

Locusts and conditions

  • Locust densities remained generally low in surveyed areas of Central Highlands Regional Council (RC).
  • Surveys of the Springsure–Buckland Plains area in mid-March identified Isolated density adults and Present–Numerous density late instar nymphs. Scattered density adults were recorded in the Rolleston–Arcadia Valley area.
  • There was light–moderate rainfall (<20-40 mm) in Isaac RC area during the first week of March and patchy light-moderate falls in Isaac and Central Highlands RC areas in mid-March. Pasture vegetation is drying off in much of the region.

Forecast

  • Nymphs in the Springsure area will have fledged in late March, but are only likely to maintain the overall low regional population density.
  • At this stage in the season there is a low probability of any significant breeding or large population increase during April or May.
  • There is a low probability of any significant immigration from other regions during April or May.

Risks

  • There is a low risk of a widespread infestation developing during autumn or spring.

South Central & Darling Downs

Balonne, Murweh and Paroo Shire. Maranoa, Western Downs and Goondiwindi Regional Council

Locusts and conditions

  • Locust density remained generally low in surveyed areas during March, but some localised breeding has occurred in recent months.
  • Surveys were conducted in the northern parts of Murweh Shire and Maranoa regional Council (RC) area in mid-March. Isolated–Scattered density adults were identified in most areas, with occasional Present density mid- and late instar nymphs near Augathella and Mitchell.
  • There was patchy light–moderate (<20-40 mm) in parts of Western Downs Regional Council (RC) area during each of the last two weeks of March. Pasture vegetation is drying out in most of the region, but remained green in the Mitchell–Injune area.

Forecast

  • Nymphs will have fledged in late March but are unlikely to have contributed to a large population increase. Habitats suitable for further breeding are now restricted to the northern districts of the region.
  • There is a low probability of further breeding or of a significant population increase during the remainder of autumn. Any eggs laid in April will enter diapause and hatch in early spring.
  • There is a low probability of significant immigration from other regions during April or May.

Risks

  • There is a low risk of a widespread regional infestation during autumn or spring.

Locust activity should be reported to Biosecurity Queensland (Queensland Department of Agriculture and Fisheries) on 132 523. A toll free call to the APLC can be made on 1800 635 962. An answering machine is attached for after-hours calls. Reports can also be e–mailed to APLC or sent through the web page at Australian Plague Locust Commission.

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South Australia

Far North, Northeast, Northwest & Western Agricultural Region

Locusts and conditions

  • Several periods of migration activity resulted in a redistribution of population in the northern regions during March.
  • There were reports of increased locust numbers and subsequent declines at Port Augusta, Innamincka, Dulkaninna and Hawker–Parachilna during the first half of the month.
  • Surveys were conducted in parts of the Far North and Northeast regions in late March. Scattered–Numerous adults were identified in the Parachilna and Murnpeowie–Dulkaninna areas, and Isolated–Scattered density adults in the Yunta–Orroroo area, but only occasional adults were recorded in other areas. No nymphs were detected by surveys.
  • The Dulkaninna light trap recorded 25–70 locusts during 12–15 March and low numbers on 28 and 29 March. None were recorded at the Oodnadatta light trap.
  • There was widespread moderate–heavy rainfall (20->40 mm) in these regions during 8–16 March and further localised light–moderate falls in the Northwest region during 17-24 March. Vegetation in locust habitat areas is now green in parts of the Far North and Northwest regions.

Forecast

  • Rainfall in the Far North and Northwest regions produced suitable soil and vegetation conditions for locust breeding. Light trap data and reports indicate adult activity in the Far North coincident with the rain in mid-March, so some aggregation and localised high density egg laying was therefore possible, particularly in the Clifton Hills–Mungerannie and Cordillo Downs–Cadelga areas, in similar locations to the January breeding event. Any eggs in mid-March could produce a split cohort of diapause and developing eggs that would hatch during April. A larger proportion of eggs laid from late March will enter diapause dormancy. This would reduce the size of a potential late autumn nymph population, but could result in some nymphs developing in early spring. Any egg laying in the Northwest region is more likely to be at low densities, despite green vegetation, as current adult densities are likely to be low.
  • Sporadic egg laying may have occurred in parts of the Northeast region or Eyre Peninsula. Localised low–medium density nymphs could develop in some areas during spring.
  • There is a moderate probability of further redistributions or small movements to adjacent regions in South Australia during April, but there is a low probability of significant population increases as a result.

Risks

  • There is a low risk of widespread regional infestations developing during autumn or spring.

Murray Valley, Mt Lofty Ranges & Southeast Region

Locusts and conditions

  • The locust population densities remained generally low during March.
  • Surveys of the Jamestown–Burra–Morgan–Renmark area in mid-March recorded Isolated–Scattered density adults. Numerous density young adults and late instar nymphs were recorded at one location near Jamestown.
  • There was light–moderate rainfall (<20-40 mm) in parts of the Murray Valley region during 8–16 March.

Forecast

  • There is a low probability of a significant population increase during autumn.
  • There is a low probability of any significant immigration during April or May.

Risks

  • There is a low risk of an infestation developing during autumn or spring.

Locust activity should be reported to Biosecurity SA (Primary Industries and Region South Australia) on the Locust Reporting Hotline on 1300 666 101. A toll-free call to the APLC can be made on 1800 635 962. An answering machine is attached for after-hours calls. Reports can also be e–mailed to APLC or sent through the web page at Australian Plague Lo​cust Commission.

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Victoria

North West & North Central Victoria

Locusts and conditions

  • Locust population remained at generally low densities, but numbers increased in parts of the North Central and Northwest regions, following small immigrations from adjacent areas of NSW.
  • Low density adults were reported near Kerang and Echuca on 10 March and medium density adults near Mitiamo on 22 March. These events coincided with the passage of low pressure weather systems.
  • Surveys in mid-March along the Murray River corridor from Echuca to Kerang identified only Isolated density adults, and Isolated–Scattered density adults in the northern Mallee district.
  • There was localised light–moderate rainfall (<20–40mm) in parts of Northwest and North Central Victoria in mid-March. Pastures remain dry in most areas.

Forecast

  • The locust population is expected to remain at generally low densities during autumn, despite the immigrations during March. There is a moderate probability of further low density movements from the Riverina or Far Southwest NSW during April.
  • Adults are likely to persist in some areas during April and May, and could congregate on irrigated pastures. Some localised low density egg laying is likely to occur, but eggs will enter diapause dormancy and not hatch until October. Nymphs, mostly at low densities, could develop in some areas in October and November.
  • There is a low probability of significant immigration into Victoria during April or May.

Risks

  • There is a low risk of a widespread infestation developing during autumn or spring.

Locust activity should be reported to Department of Economic Development, Jobs, Transport and Resources on 1300 135559. A toll-free call to the APLC can be made on 1800 635 962. An answering machine is attached for after-hours calls. Reports can also be e–mailed to APLC or sent through the web page at Australian Plague Locust Commission.

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Glossary of locust terms and density categories used in the Locust Bulletin

Locust biology and behaviour

TermDefinition
adultA fully winged, mature locust capable of breeding and migrating
bandDense aggregation of nymphs, usually moving forward together
diapausePeriod of dormancy in anticipation of unfavourable environmental conditions
egg bedAn area of soil containing many egg pods (up to 1000 per square metre)
fledgeFinal nymphal moult to a soft-bodied adult incapable of long-distance flight
instarDiscrete stages of nymphal development each separated by a moult
layingFemale locusts each depositing clutches of 20-60 eggs into the ground in froth-lined egg pods
nymphJuvenile wingless locust. Often referred to as the hopper stage
swarmDense aggregation of adults, milling at the same spot or flying closely together

Locust density categories

Where higher densities occur, a large proportion of the regional population is concentrated in very small areas with lower densities elsewhere, so the higher densities cannot be extrapolated over the area of an entire region. A range of density classes is usually found within a surveyed region.

Nymph DensitiesNumber per m2
Present1 – 5
Numerous6 – 30
Sub–band31 – 80
Band> 80

Adult DensitiesNumber per m2Number per hectare
Isolated– 0.02< 200
Scattered0.03 – 0.1> 200 – 1000
Numerous0.2 – 0.5> 1000 – 5000
Concentration0.6 – 3.0> 5000 – 30,000
Low Density Swarm4.0 – 10> 30,000 – 100,000
Medium Density Swarm11 – 50> 100,000 – 500,000
High Density Swarm> 50> 500,000

General density classesNymph densitiesAdult densities
very low, occasionalNil–PresentNil–Isolated
lowPresentIsolated–Scattered
mediumNumerous—Sub–bandScattered–Numerous
highBandsConcentration–Swarms

Reporting locust infestations

It is important that all locust activity is reported as soon as possible to your nearest state agriculture agency office or to the Australian Plague Locust Commission.

StateAuthority for reporting locusts
New South WalesLocal Land Services (LLS) or Department of Primary Industries
QueenslandBiosecurity Queensland, Department of Agriculture and Fisheries
South AustraliaBiosecurity SA, Primary Industries & Regions South Australia (PIRSA)
Victoria

Biosecurity Agriculture, Department of Economic Development, Jobs, Transport and Resources

Reports to the Australian Plague Locust Commission can be made by:
Free call (Canberra): 1800 635 962 (24 hours)
Fax (Canberra): (02) 6272 5074
E–mail: APLC
Internet: Australian Plague Locust Commission

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