Locust Bulletin April 2019

​​​​​​​​​​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 forecasts and maps of locust distributions.

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General situation in March and outlook to Spring 2019

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Australian plague locust - Chortoicetes terminifera

The locust population level remained very low and in decline over most inland regions due to generally ongoing drought conditions in most of eastern Australia. A moderate population increase previously identified in the Central West and Northwest Plains of New South Wales appears to have declined. Locust numbers remained low in NSW, with almost no counts in Victoria and South Australia. Low numbers were also recorded from the Channel Country up to Central West Queensland. No nymphs were identified in any surveys in March and habitat conditions remained very dry. There were no evidence of any significant locust activities.

Surveys in parts of the Central West of New South Wales indicate that the previous medium-density adult locusts in the Coonamble district had declined. A suitable weather system in mid-March may have encouraged some short-distance emigrations from the Coonamble region. Survey of the Riverina and Far Southwest regions only found very low density of adult populations.

Survey in Northwest Victoria did not detect any individuals. Locust numbers are expected to have remained very low in inland habitats. The population in the Omeo Valley and Swifts Creek areas in East Gippsland are expected to have persisted.

Surveys conducted in South Australia detected only very low numbers in the northeast corner of the state. Some floodwaters entered from Queensland from mid-February but had so far only produced limited vegetation response along the affected drainage systems.

Surveys in Queensland identified occasional adults in the Southwest and Central West regions, but no nymphs were detected. Flooding in the Northwest generated some green vegetations downstream along the affected channels in the Southwest, where survey access was restricted, but large areas of the Southwest remained dry before the landfall of Cyclone Trevor. Despite the widespread heavy rain associated with the ex-cyclone in late March, locust numbers are expected to remain low due to the current low background population level. However the wet conditions and subtropical climate may stimulate some late breeding. The locust situation in Queensland will be closely monitored throughout autumn.

The outlook for the remainder of autumn is for continuing low population densities in most regions of inland eastern Australia. However, widespread heavy rainfall in Queensland in late March will produce favourable habitat conditions for locusts. Egg laying could occur during April and May, and an extra generation could therefore be produced in subtropical areas of Queensland. However, as the current population level is so low, there is only a low probability of any significant population increase in the short term, nor a high-density of nymphs in spring in inland regions where egg laying could take place.

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

5 April 2019

Spur-throated locust - Austracris guttulosa

The population level remains extremely low this season. Only two isolated adults were detected in Central West Queensland during surveys in March, but none were recorded in any other areas surveyed.

Heavy rainfall in the Northwest, Central West and Gulf regions of Queensland at the start of February may have provided some suitable habitats for breeding, but no adults or nymphs were detected in the Southwest where floodwaters generated green vegetation. Adult females can produce several pods and egg laying is often initiated by rainfall. However, the very low known adult population prior to the rains and late commencement of any breeding, indicate that a large autumn nymph population is very unlikely. With the additional widespread rainfall in late March, possible egg laying could occur in April and hatchings could commence during April with adult fledgings in late May to June. Locust habitat in the Central Highlands region was mostly dry but received some rainfall in the second half of March with the population level not expected to increase dramatically.

There is a low risk of a widespread infestation developing during 2019.

Migratory locust - Locusta migratoria

This species has not been detected since October 2018, when very low numbers were recorded in the southern Central Highlands region of Queensland. Rainfall in parts of Central West and Northwest Queensland in early February could have initiated some breeding that would contribute to maintaining overall very low population densities.

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

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.

Locust distribution map – Chortoicetes terminifera

Map of Australian plague locust distribution 4 March to 31 March 2019

Australian plague locust (Chortoicetes terminifera)

Situation in March and forecast to Spring 2019

New South Wales

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Central West and Northwest Plains
Central West, Northwest and Central Tablelands Local Land Services

Locusts and conditions

  • Only isolated adults were recorded in the surveyed southern part of this region in contrast to previous Scatted to Numerous densities.
  • There were no further reports from areas in the northern Central Tablelands or Hunter LLS areas where locusts developed during January.
  • There was moderate – heavy rainfall (50 – 100 mm) in the Nyngan–Coonabarabran-Dubbo area during the second half of March. There was some localised green vegetation response in these areas, but conditions in most areas remained dry.

Forecast

  • The previously identified medium density of the adult locusts in early February in the Coonamble–Collie–Baradine area appears to have declined, as there was a favourable weather system (trough) for matured locust adults to emigrate in mid-March, and only isolated adults were recorded in adjacent areas afterwards.
  • The low adult numbers are expected to persist, given the late March rainfall which will generate a lush vegetation response. However, the population level is not expected to increase significantly as day length is getting shorter and temperature is decreasing.
  • The localised low-density adult population could produce some eggs after the late March rainfall. However, any eggs laid from now would suspend further development, and nymphs will not hatch until September. Therefore Present–Numerous densities are likely to develop in spring.
  • There is a low probability of significant immigrations from other regions during autumn, but some redistributions are possible within these regions.
  • April survey of these areas is scheduled.

Risks

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

Riverina
Riverina and Murray Local Land Services

Locusts and conditions

  • The localised low-moderate population identified in the Lake Cargelligo area was found to be persistent with the adult density in February.
  • The locust population remained at low density in Hay-Narrandera-Deniliquin area while surveys of other areas recorded no locusts at all.
  • There were no locust reports and habitats remained very dry. The insect monitoring radar in Hay did not detect any locust migration activities.
  • There was patchy light rainfall (<20 mm) in the southern Riverina in late March. Pasture vegetation remained dry in most districts.

Forecast

  • The localised population in the Lake Cargelligo area is likely to persist in the region, and the general population level will remain low in the Riverina during autumn.
  • Sporadic low-density egg laying is possible after the late March rain. However, any eggs laid will remain in diapause and hatching will not commence until late September. Only localised low-density nymphs are likely to develop in spring.
  • There is a very low probability of significant immigration from other regions during autumn.

Risks

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

Far West and Far Southwest
Western Local Land Services

Locusts and conditions

  • Surveys in the Far Southwest detected only a few Isolated adults in the Ivanhoe-Hillston and Scotia-Wentworth regions.
  • The Fowlers Gap and White Cliffs light traps recorded no locusts. The insect monitoring radar in Bourke did not detect any locust migration activities. In addition, other airborne insects were only observed at extremely low numbers, indicating general conditions were extremely poor over a large area.
  • There was localised light rainfall (~20 mm) in Broken Hill district during late March, while most of the region received much less. Pasture vegetation remained very dry in most areas.

Forecast

  • The very low current population level and ongoing dry habitat conditions in most areas indicate that locust numbers are very likely to remain low during autumn and spring.
  • Only very low-density egg laying is possible in the areas that received localised rainfall and only occasional nymphs are expected in spring. Any eggs laid after the late-March rain will enter diapause. Any expected hatchings would commence in late August in the Far West and mid-September in the Far Southwest.
  • There is a very low probability of significant immigration from other regions during autumn, given the very low population in possible source areas.

Risks

  • There is a low risk of a widespread 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.

Queensland

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Southwest
Barcoo, Bulloo, Quilpie and Diamantina Shire

Locusts and conditions

  • The locust population remained low in areas surveyed, only occasional adults and no nymphs were detected. Access to western areas was limited by flooding but vegetation responses only appeared along the flooded drainage lines.
  • No locusts were recorded at the Birdsville or Nooyeah Downs light traps. There were no reports of locust activity.
  • There was heavy rainfall (>40 mm) brought into this region associated with ex-Cyclone Trevor in late March; more than 200mm fell in some areas of Boulia, Winton, and Windorah districts. Vegetation was already green before the late March rainfall in Barcoo, Quilpie, Bulloo and Diamantian shires where moderate-heavy rainfall was received in early February and as floodwaters travelled down the Cooper Creek and Diamantina River systems in late February.

Forecast

  • Locust numbers are expected to remain generally low during autumn. However, areas that received sufficient rainfall have produced suitable vegetation and soil conditions for locust breeding, particularly in Barcoo, Quilpie and northern Diamantina shires. Sporadic, low-density egg laying is likely given the very low pre-existing population level. Egg laying could have commenced in late February and might continue during April.
  • Any eggs laid in February would have hatched from mid-March. However, the heavy rainfall and floods may have hampered locust breeding. The majority of eggs laid from mid-March onwards will enter diapause. Some nymphs may hatch in late autumn, and thus an extra generation is possible in this sub-tropical region.
  • Diapause eggs would remain in dormancy and nymphs will hatch in mid-August. Localised Numerous density nymphs could develop but high-density nymphs or bands are unlikely based on the current low background population.
  • There is a low probability of significant immigration from other regions during autumn, but short-range redistributions may occur in this region.

Risks

  • There is a low risk of a widespread infestation developing during 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

  • Surveys were conducted in the Central West while the Northwest was inaccessible. Isolated density adults were identified in Longreach and Blackall-Tambo RC areas.
  • No locusts were recorded at the Longreach light trap during March.
  • Recent reports had been received from properties between Winton and Muttaburra and these properties were inspected in early April. There were consistent high-density (Concentration to Low Density Swarm) other species of grasshopper, most Peakesia spp., in late instar and adult stages, but only very rare locust adults among them. About 50% female grasshopper adults had 2mm eggs on board and damage to pasture was substantial.
  • There was heavy (50 - 200 mm) rainfall in these regions in late March, associated with ex-Cyclone Trevor. Some locations received a monthly total of up to 300 mm. Vegetation had become green since February.

Forecast

  • Locust numbers are likely to remain generally low during the autumn, but nymphs could develop in some areas. Egg laying might have occurred since late February and continue into April, but the very low prior population level suggests most would have been be at low densities.
  • A proportion of eggs laid after mid-March will enter diapause and nymphs will hatch in August and September. Most hatchings will be at low densities, but some Numerous or higher density nymphs could develop in localised areas in autumn and spring.
  • There is a low probability of significant immigration from other regions during autumn. Increased adult population numbers in late autumn are unlikely to pose a migration risk to regions in NSW or South Australia.

Risks

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

Central Highlands
Central Highlands and Isaac Regional Council

Locusts and conditions

  • No surveys were conducted in this region in March and there were no reports.
  • There was some very heavy rainfall (>100 mm) in this area in the second half of March. Clermont received more than 200 mm within these two weeks. Pasture vegetation was dry before the substantial rains in most areas.

Forecast

  • The locust population level is likely to remain generally low during autumn. The large amount of March rainfall could initiate sporadic low-density breeding and nymphs could develop in localised areas in April. Most eggs laid during April will enter diapause and nymphs hatch from late August.
  • There is a low probability of a large population increase during autumn or spring.
  • There is a low probability of immigration from other regions during autumn.

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

  • Only limited surveys were conducted in the South Central. Occasional Isolated adults were detected only in the north, and vegetation was dry to the south.
  • There were no reports.
  • There was very light rainfall (<20 mm) in mid-March, but moderate–heavy rainfall (>100 mm)  associated with ex-Cyclone Trevor. Southern areas received much less rainfall (<20 mm) during the period.

Forecast

  • The locust population is likely to remain low during autumn and winter, with only limited opportunities for breeding.
  • Any eggs laid from now will enter diapause and nymphs will not hatch until September.
  • There is a low probability of immigration from other regions during autumn.

Risks

  • There is a low risk of a widespread infestation developing 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.

South Australia

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Far North, Northeast, Northwest & Western Agricultural Region

Locusts and conditions

  • Surveys were conducted in the eastern part of this region, in Northeast and Far North. Only occasional Isolated adults were detected in the northeast corner of Far North, where floodwaters entered from Southwest Qld. Apart from flooded creeks (since mid-February), habitats were very dry.
  • There were no reports.
  • The Dulkaninna and Oodnadatta light traps did not record any locusts during March.
  • There was only light to moderate rainfall (<20 – 40mm) in these surveyed regions in late March.

Forecast

  • The locust population level is likely to remain very low in these regions during autumn. The current very low numbers and dry habitats will limit opportunities for any breeding.
  • There is a low probability of migrations into these regions during autumn.

Risks

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

Murray Valley, Mt Lofty Ranges & Southeast Region

Locusts and conditions

  • Surveys conducted in Murray Valley detected no locusts.
  • There were no reports.
  • There was very little rainfall in these regions. Vegetation was dry in most areas.

Forecast

  • The locust population level is likely to remain very low during autumn.
  • There is only low probability of any immigration from other regions during autumn.

Risks

  • There is a low risk of a widespread 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 Locust Commission.

Victoria

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Northwest & North Central Victoria

Locusts and conditions

  • Limited survey conducted in the Northwest did not detect any locusts.
  • There was light rainfall (<20 mm) in Northwest Victoria in late March. Vegetation remained dry in most areas.

Forecast

  • Locust numbers are likely to remain low in inland areas during autumn. Given the very low background population in most areas, any sporadic breeding will be at low density. The majority of any eggs laid from early March would have entered diapause. Nymphs would hatch from early October in the north to mid-October in southern areas.
  • The locust population in the Omeo Valley is likely to persist during autumn with egg laying likely in some areas. At this stage the size of the autumn breeding locust population relative to other species present in the area is uncertain, but if aggregation and egg laying occur, nymphs could develop at Numerous or higher densities in some areas during spring.
  • There is a low probability of significant immigration from other states during autumn.

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)
VictoriaBiosecurity 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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