Locust situation 06 January 2023
This page summarises the known distribution of locusts during December 2022 and provides a brief outlook to March 2023. This is an interim advice in lieu of the regular monthly Locust Bulletin.
The locust population remained at generally low levels across inland eastern Australia – except for the Broken Hill-Peterborough-Mildura-Ivanhoe areas where persistent Numerous – Low-Density Swarm adults and occasional Numerous-density nymphs were identified. Surveys in December also identified some Isolated – Scattered-density adults with only occasional Present-density nymphs in the Broken Hill-Tibooburra-Wilcannia areas of New South Wales and the Hughenden-Mount Isa-Urandangi-Boulia-Longreach areas of Queensland. No surveys were conducted in December in other regions due to widespread flooding preventing access. The light traps at White Cliffs (NSW) and Dulkaninna (South Australia) captured several hundred locusts in late December, reflecting some congregation and/or short-distance movement associated with storm weather events and the passage of low-pressure systems in the southern part of inland eastern Australia where several reports of locust activity were received.
December rainfall was below 25 mm over much of inland eastern Australia, though, 50-100 mm of rainfall was recorded in the north-eastern parts, generally reflecting average levels. December temperatures remained below average across much of the inland area, with cooler temperatures (1-3 degrees below average) in the eastern parts and lowest on record experienced in the NSW Central West district. The slowly weakening La Niña is expected to influence inland areas during the remainder of summer, but average rainfall and warmer temperatures are likely for January to March – except for the eastern part in NSW where below average maximum temperatures are likely.
The outlook for January to March is for a moderate population increase to medium density levels with some localised areas of higher density possible from current low background populations in the arid and semi-arid interior areas plus persistent medium – high-density populations in southern parts of inland eastern Australia. Further medium density populations are possible after any successful breeding in the northern and north-eastern parts of inland areas.
Adults will continue to form swarms associated with congregation and redistribution in areas experiencing hot weather. These are most likely to occur in the southern portion of inland areas. Daylight dispersal and night migration can be facilitated by suitable weather at the appropriate stage of locust development, possibly trending more towards the interior. Hatching should commence in early 2023 with some summer generation bands likely to develop in southern parts, possibly continuing into February. Localised breeding may also occur in other parts of the inland producing some higher densities. Summer generation adults should start fledging from early February onwards in southern parts, with overlapping generations likely to appear in the interior.
There is a moderate likelihood of region-wide infestations developing in the SA Flinders, North East Pastoral and Riverland districts, NSW Upper Western, Lower Western and Riverina districts, and Mallee district of Victoria. Widespread high-density infestations are unlikely between now and early autumn.
The overall population was at low to medium levels. Surveys in December identified consistent Scattered to High-Numerous density adults in the Hughenden-Urandangi-Boulia-Longreach areas of Queensland with Present – Numerous-density nymphs, and occasional Isolated-density adults in the Upper Western and Lower Western districts of New South Wales. The light traps at Dulkaninna (South Australia) and White Cliffs (New South Wales) captured some locusts in December, indicating the presence of local background populations. Suitable habitat conditions will encourage localised breeding that could result in medium density nymphs.
There is a medium risk of a widespread low-medium density infestation. Some localised high-density infestations may develop in Queensland between now and early autumn.
The population is likely to remain at a very low level. Surveys in December did not detect any migratory locusts. Localised breeding should continue under favourable habitat conditions, but below average December rainfall may have discouraged breeding in some parts of subtropical areas. Nevertheless, high-density infestations are unlikely to result from the current very low population level.
There is a very low risk of a widespread infestation developing between now and early autumn.