Current locust situation
Locust situation 03 January 2021
This page summarises the known distribution of locusts during December 2020 and provides a brief outlook to March 2021. Regional information and forecasts are given in the latest locust bulletin.
Australian Plague Locust (Chortoicetes terminifera)
The locust population remained at a low to medium level over most of inland eastern Australia, with some higher densities regularly detected in various parts of New South Wales and Queensland. Populations were geographically fragmented and often transient, with many exhibiting overlapping life-stages. Surveys in December identified swarms in the Riverina of New South Wales, and Southwest and South Central Queensland. Localised bands were detected in the Far Southwest of New South Wales while occasional nymphs were observed or reported across several locations in New South Wales and Queensland where consistent low to medium numbers of adults were detected by surveys. Frequent short-distance redistributions were evident in Queensland and New South Wales, but no suitable weather systems occurred to facilitate any long-range migrations. No surveys were conducted in either Victoria or South Australia, and no reports were received, but locust populations are expected to have remained at generally low levels in both States based on previous population sizes and December rainfall.
December rainfall was generally about average across much of inland eastern Australia, but above average was recorded in the north-eastern areas and a little below average in the southwest. Temperatures exhibited a similar pattern, where inland Queensland was about 1–2 degrees higher than average while the southwest was slightly below average. Localised moderate-heavy rainfall (>25 mm) was received in Miles and Moonie (3/12), Adavale and the Goondiwindi-Moree-Armidale areas (4/12), Isisford, Jundah, and Emmet (12/12), Swan Hill (17/12), Clermont and Emerald (19/12), Jundah, and the Hungenden-Winton areas (26/12), plus widespread light-heavy rainfall (10-100 mm) across much of the inland during 21-22 December. The La Niña event is likely to have peaked at a moderate level, but above average rainfall and temperatures are still expected in much of inland eastern Australia during the remainder of summer.
In New South Wales, the nymphal populations of the summer generation identified were much lower than expected from previously observed large and dense swarms despite intensive effort. Only one Low-Density Swarm was identified in the Lake Cargelligo district while consistent Isolated to Numerous-density adults were identified in the Far Southwest and adjacent north-western areas of the Riverina, with localised Present to Band-density nymphs in the Darnick district. These nymphs would have hatched from eggs laid in late November. Aerial surveys were conducted with ground verification during 07-10 December but did not confirm any significant bands in the Central West and Far Southwest regions. Frequent tropical troughs penetrated the interior of New South Wales and encouraged short-distance redistributions of adult locusts.
In Queensland, Isolated to Numerous-density adults were detected in surveys of South Central, Central West and Southwest with Concentration to Medium-Density Swarms of adults in the Cunnamulla, Windorah and Augathella districts. Only a few nymphs were identified. Disturbed weathers may have redistributed and aggregated locust adults as there were sudden appearances and dis-appearances of adult locusts in the Roma-Goondiwindi-Dalby areas in early December.
The outlook for January is for increasing locust activity, with a high likelihood of further successful widespread breeding in Queensland and New South Wales but only limited to localised, sporadic breeding in other States. It is expected that more bands and swarms will develop from January onwards and result in a larger summer population with further multiplication potential in autumn.
There is a moderate likelihood of more widespread high-density populations and region-wide infestations developing during summer and early autumn.
Spur–throated Locust (Austracris guttulosa)
Surveys in early and mid-December only detected low occurrences of Isolated–Numerous densities of adults in the South Central and Central West Queensland and only Present density nymphs in the Longreach district.
The above average rainfall and temperatures in much of the Queensland interior in December may have initiated some localised sporadic breeding. Seasonal breeding appears to be delayed by the later rainfall but low-density nymphs are still likely to appear in much of Queensland with some localised medium to high-density populations expected to occur in the Central Highlands region. 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 a region-wide infestation in subtropical Queensland developing during the remainder of summer and early autumn.
Migratory Locust (Locusta migratoria)
Surveys in December did not detect any migratory locust, but the locust habitat conditions in the Central Highlands of Queensland remained reasonably favourable and recently improved further. Under the influence of the current La Niña event, localised breeding is likely to 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 the remainder of summer and early autumn.
Locust forecasting regions