Current locust situation

Locust situation 06 April 2021

The following Update is issued as an interim advice in lieu of the regular monthly Locust Bulletin. Full details of locust populations and forecasts for regions are not available as ground surveys have not been possible since early March due to widespread and repeated rain received in critical locust population areas.

Surveys will resume as soon as weather and ground conditions permit. Once additional field population information is available, a full detailed Bulletin will be prepared.

March rainfall was from a few millimetres to more than 200 mm over many parts of inland eastern Australia, varying from average to highest on record. The Queensland Channel Country and surrounding areas, where large locust adult population was previously identified, received at least 25 mm to over 50 mm rainfall, with habitat conditions likely to improve significantly as a consequence. Quilpie airport recorded 62.4 mm on 23 March and its March total was 97.7 mm, while Boulia received 28.8 mm and Bedourie 78.4 mm rainfall for March. Daily maximum temperatures were from above average in the northern part to very much below average in the southern part of the interior, and daily minimum temperatures were average over much of the interior with below to very much below average in central New South Wales. Thus, monthly mean temperature was below to very much below average in the interior of New South Wales. The La Niña event has ended, and rainfall and temperatures are expected to return to normal patterns. Drier than average is likely over much of the inland for April and May. Maximum temperatures are likely to be above the median in April and May, but minimum temperatures are likely to be lower than the median.

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Australian Plague Locust (Chortoicetes terminifera)

The Australian plague locust population persisted at a medium to high level in the south-eastern part of inland eastern Australia, and most likely remained at similar levels in the north-western part. Widespread rainfall and floods hampered ground survey of areas where large locust populations had previously been identified. Surveys in early March identified Numerous – Low-Density Swarm adults in the Ivanhoe-Lake Cargelligo-Jerilderie areas of the New South Wales Riverina and surrounding areas, with some late instar nymphs also detected. Isolated – Scattered-density adults were observed in mid-March in the Central West, Central Highlands and Coalfields, and Maranoa and Warrego regions of Queensland, with occasional nymphs detected. Slightly higher numbers were identified in the Winton district, but no bands were visible in the Longreach-Windorah-Bedourie-Boulia-Winton areas during aerial surveys at the end of March. Weather patterns, detections by the insect monitoring radar in Hay, and light-trap captures in White Cliffs, Fowlers Gap and Dulkaninna indicate several occurrences of short-distance migration during the March, with likely redistributions of the adult population. No surveys were conducted in South Australia or Victoria, and no reports were received from these two States. Locust populations are expected to remain at low levels in both States.

The April outlook is for persistent locust activity, with a high likelihood of further successful widespread breeding in the southwest of Queensland and adjacent areas of South Australia and New South Wales, but only limited to localised, sporadic breeding in other regions. It is expected that more bands will develop and result in a larger autumn population in the north-western part of the inland, while eggs laid from mid-March onwards will either enter diapause or slowly develop during winter.

There is a moderate likelihood of more widespread high-density populations and region-wide infestations developing in the southwest of Queensland during the remainder of autumn.

Spur–throated Locust (Austracris guttulosa)

Surveys in mid-March detected consistent occurrences of Isolated – Numerous-density adults and Present -density nymphs in the Clermont-Roma areas of Queensland, with frequent Present-density nymphs in addition to sparse Isolated – Numerous-density adults in the Longreach-Winton areas. Only occasional adults were identified in New South Wales.

With sufficient rainfall and warmer autumn temperatures in tropical and sub-tropical Queensland, low-density nymphs are still likely to appear and result in some localised medium to high-density populations. Only limited breeding is likely in New South Wales and South Australia based on their very low background populations.

There is only a low risk of a widespread infestation, but the possibility exists for localised higher density infestations to develop in subtropical Queensland during the remainder of autumn.

Migratory Locust (Locusta migratoria)

Surveys in mid-March detected Isolated – Scattered-density adults in the Clermont-Injune areas of Queensland. Improved habitat conditions in the Central Highlands and Coalfields and the Darling Downs and Granite Belt regions of Queensland, any localised breeding could possibly produce some low to medium density populations. High-density gregarisation is unlikely to result from the current very low background level.

There is a very low risk of a widespread infestation developing during remainder of autumn.

Last reviewed: 6 April 2021
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