Current locust situation

The locust population increased moderately in inland eastern Australia. In addition to the persistent higher numbers in the Riverina district of New South Wales, population levels increased markedly in the arid interior.

Surveys in March identified consistent Scattered – Numerous-density adults in parts of the Channel Country of Queensland, with Isolated-density adults present in other parts of Queensland. Some Present-density nymphs were also detected in parts of the interior of Queensland. Surveys in South Australia identified two large Low-Density swarms of young adults in the Moomba area and frequent Numerous-density adults in north-eastern parts of the North East Pastoral district. Isolated-density adults with occasional Scattered density were detected in other parts of SA. A small band and several Sub-Band density nymphs were identified in the north Flinders Ranges with Present-density nymphs present in other parts of SA. Surveys in New South Wales identified persistent Scattered – Numerous-density adults in the Riverina district with some Present – Numerous-density nymphs detected. Constant Numerous-density adults were identified in the western part of Upper Western district with no nymphs detected. No locusts were detected in the North West and Central West districts. No surveys were conducted in Victoria but several reports were received from the north-western Victoria. The light trap at Fowlers Gap caught locusts on most nights with a peak capture in late March when 10 fold more were recorded at Dulkaninna but nil at White Cliffs. The insect monitoring radar at Hay detected several northward migrations in early and mid-March. The significant population increase in the arid interior of eastern Australia reflects a successful breeding of populations that redistributed and aggregated after the record rainfall event during late January – early February. The proportion of diapause eggs laid after mid-March increases with latitude and time, i.e. higher diapause rates of eggs would be laid by the adults in the southern part of inland eastern Australia towards the end of March.

March rainfall ranged from nil (west) to 100 mm (east) over inland eastern Australia and rated as average level generally with some areas at above average and very much above the average levels. Much of the arid interior received less than 25 mm rain. March mean temperatures were above average over much of inland eastern Australia with northern part more than two degrees above averages. The La Niña event has weakened slightly but still influences the weather and climate, with above median rainfall and cooler daytime temperatures forecast for April. Winter is forecast to have average rainfall but warmer temperatures. Vegetation conditions are likely to remain suitable for locust breeding over most parts. The spring outlook is for a persistent moderate population with medium and localised high densities in the Riverina district of NSW and adjacent areas of the Lower Western district of NSW and the Mallee district of Victoria, plus some low to moderate populations with limited localised higher densities in other parts of inland eastern Australia. The overall locust population is likely to be at a low – moderate level in inland eastern Australia in the beginning of season 2022-23.

Some nymphs are likely to hatch from overwintering eggs in August and persist under favourable habitats in the sub-tropical Queensland where above average winter and spring rainfall is received. Localised high-density nymphs may develop from diapause eggs in the Riverina and adjacent areas from late September onwards. It is expected that some bands may develop and result in localised high-density spring populations in the Riverina and surrounding areas, with some early low – medium density nymphs in Queensland.

There is a low likelihood of widespread high-density populations and region-wide infestations developing in spring, but possible localised high-density populations and limited infestations may develop in parts of NSW.

The population of Spur-throated locusts increased moderately in inland eastern Australia during March 2022. Surveys identified consistent adults of Isolated – High-Numerous densities with higher numbers in the northern part, plus Present – Numerous-density nymphs amongst which late instars were dominant but with all instars presented. The staggered instar stages reflect an extended breeding season. Nymphs were mainly found in Queensland. No reports were received but some adults were captured in APLC light traps. With suitable habitat conditions, existing nymphs should survive and may develop into some localised medium-high density adult infestations.

With a wet April expected in tropical and subtropical Queensland, a higher nymphal survival rate is likely and should result in more localised medium – high-density adults in the remainder of autumn and winter.

There is a medium risk of a widespread low-medium density infestation, and localised high-density infestations are likely to develop in affected areas of subtropical Queensland in the remainder of autumn and winter.

Surveys in March only identified a single occurrence of adult migratory locusts in the Darling Downs district of Queensland. However, under current favourable habitat conditions, breeding should have continued in the Central Highlands and surrounding areas of Queensland. Nevertheless, high-density gregarisation is unlikely to result from the previously very low population level.

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