This page summarises the known distribution of locusts during March and provides a brief outlook to spring 2018. Regional information and forecasts are given in the
latest locust bulletin.
The locust population level has remained low over most of its range in eastern Australia throughout the 2017-18 season. Only sporadic low density breeding occurred in most regions, maintaining the overall low population densities. Most areas that received rainfall during summer dried out rapidly and prolonged high temperatures are likely to have caused increased mortality of nymphs and adults. Surveys during March recorded low numbers of adults and occasional nymphs in the Central West, Central Highlands and South Central regions of Queensland. Only occasional adults were recorded in most areas of the Riverina, Far Southwest and southern Central West regions of New South Wales.
In New South Wales, surveys of the Far Southwest, Riverina and Central West regions in mid-March identified only occasional low density adults in most areas. Medium–high density adults and occasional late instar nymphs persisted in a small area of residual green habitat in the Lake Cargelligo area of the southern Central West.
In Queensland, surveys of the Central West, South Central, Central Highlands and parts of the Northwest regions identified occasional adults in most areas. Low density adults and mid-instar nymphs were identified in the South Central region in mid-March, indicating some breeding occurred in early February. Heavy rainfall in early March across most regions produced favourable habitat. Further storm rains and flooding of inland rivers will maintain green vegetation throughout autumn and early winter.
In South Australia, survey of the Northeast and Murray Valley regions identified only occasional adults. Habitat conditions are very dry in most regions and, based on previous surveys, locust population numbers are likely to have remained very low in other areas.
Surveys in Victoria in mid-March identified low density adults in the Boort–Ouyen area, but very few locusts were recorded elsewhere in the Northwest or North Central regions.
The outlook for the remainder of autumn is for population densities to remain low in most regions of inland eastern Australia. Widespread heavy rainfall in Queensland during March produced favourable habitat conditions for locust breeding, and sporadic egg laying could continue during April and May. Aggregation and high density egg laying is unlikely, given the current very low adult numbers. However, some low density nymphs could develop during late autumn and winter in Southwest, Northwest or Central West Queensland, and diapause eggs could produce localised low density nymphs in early spring. A large population increase is unlikely this late in the locust season. The majority of eggs laid in NSW, Victoria and equivalent latitudes in South Australia during March and April will enter diapause and not hatch until spring. There a very low risk of swarms affecting any agricultural region during the remainder of autumn. There is a low risk of high density nymph infestations developing in any region during spring.
There is a widespread low density population of this species in inland Queensland. Surveys in March recorded Isolated–Scattered density adults throughout Central West Queensland and surveyed areas of Northwest, South Central and the Darling Downs regions. Low density nymphs at various development stages were detected in Richmond and Flinders shires in northern Central West Queensland. Previous surveys recorded low density nymphs at numerous locations south of Emerald in the Central Highlands, but no nymphs were detected in March. Only Isolated adults were identified in most areas of the Central Highlands, except in the Arcadia Valley where Scattered–Numerous densities were recorded.
Heavy rainfall events in the Central West, Northwest, Queensland Gulf and South Central regions of Queensland maintained favourable habitat for continued egg laying and nymph survival. However, previously recorded adult densities were low in most areas, so high numbers of nymphs are unlikely to develop in any region. Dry conditions during February are likely to have increased nymph mortality in parts of Northwest, Southwest and Central West Queensland before the widespread rainfall in early March.
Fledging of nymphs will continue during April, with the possibility of a late cohort in the Queensland Gulf Central West and Northwest regions that would fledge in May. Young adults are replacing the current breeding population, but large population increases are unlikely. The likelihood of an overall population increase in 2018 compared to 2017 has declined.
A low density population persisted in the southern Central Highlands and northern South Central regions of Queensland throughout summer and low numbers were recorded in the same areas during March. Surveys identified Isolated density adults in areas south of Emerald in Central Highlands Regional Council (RC) area and occasional adults in Banana Shire and the Maranoa and Western Downs RC areas. This species is common in these regions and rapid population increases are possible in favourable habitat. Gregarious populations can develop at local scales and are often associated with forage or cereal cropping.
Rainfall during March in the Central West, Central Highlands and South Central regions of Queensland during March has maintained favourable soil and vegetation conditions for continued breeding. An increase in overall population level in possible during autumn. Small gregarious populations could develop in localised areas during 2018. However, there is a low risk of a widespread infestation developing during late autumn or winter.