This page summarises the known distribution of locusts during September 2017 and provides a brief outlook to December 2017. Regional information and forecasts are given in the latest locust bulletin.
Locust populations declined to low densities in most regions of New South Wales, Victoria, Queensland and South Australia during autumn. Medium density adults persisted in parts of the Far North region of South Australia during March, but habitat conditions became dry. Regions in the eastern half of NSW and Queensland received moderate-heavy rainfall during March, which could have initiated some localised autumn egg laying, particularly in the NSW Central West and Northwest Plains, or in Central West, South Central and the Central Highlands of Queensland. However, there was little winter rainfall and September remained dry in all regions, so habitat conditions are unsuitable for nymph survival in most areas. Surveys during September identified only low density adults and occasional nymphs.
In New South Wales, survey of the northern Central West and Northwest Plains identified only occasional low density adults. No nymphs were detected.
Survey was conducted in the Central Highlands and parts of the Central West and South Central regions of Queensland in early September. Low density adults and occasional late instar nymphs were identified.
In South Australia, surveys in late September identified only occasional adult locusts in the Far North region and around the Flinders Ranges.
There was no survey or report information from Victoria during September. Any spring hatching will commence in mid-October.
Current locust distributions are at low background population densities. Dry habitat conditions will limit the survival of spring generation nymphs. Low soil moisture may also have left some eggs in quiescence, which could hatch after moderate rainfall. The outlook for the remainder of spring is for population densities to remain low in all regions of inland eastern Australia. Spring hatchings have been reported in parts of the Western Australian wheatbelt, including Katanning and Wongan-Ballidu Shires. Landholders have carried out some control in localised areas.
The probability of population increases during November and summer is dependent on the distribution of moderate–heavy rainfall during the next three months. Given the current very low population densities, rapid development of widespread regional infestations is unlikely during summer. However, seasonal rainfall forecast models suggest an average rainfall expectation over coming months and even isolated heavy rainfall events can result in localised large population increases.
Adult population levels in autumn 2017 were lower than those of recent years in Queensland. There was a widespread medium density population of young adults and residual nymphs in the Northwest, Central West Central Highlands and South Central regions of Queensland during March, but no swarms were identified or reported. Young adults of this species live through winter in a non-reproductive state, often forming swarms that occupy woodlands and riparian tree lines. Migrations and local swarm movements can occur during spring and early summer.
Survey in September identified only Isolated density adults in the Central Highlands and parts of the Central West and South Central regions of Queensland. Breeding does not usually commence until the onset of the northern wet season. Habitat conditions in most regions are currently unfavourable for breeding. Egg development to hatching in this species takes 3–4 weeks and nymph development a further 8–10 weeks. Females can lay multiple times during summer, usually following significant rainfall. Nymphs of this species do not usually aggregate to form cohesive bands, but can reach densities of 30/ m2 in favourable habitats.
There is currently a low risk of swarms developing or migrating into agricultural regions during the remainder of spring and summer. The outlook is for the maintenance of moderate population levels during 2017–18.
Survey of the Queensland Central Highlands and the northern South Central region during September identified low density adults at several locations south of Emerald. Isolated density adults were recorded in the Rolleston and Taroom–Roma areas but no nymphs were detected. Populations of this species are commonly found in these regions and rapid population increases are possible in favourable habitat. Gregarization can occur at local scales and is often associated with forage or cereal cropping.
Small gregarious populations could develop in localised areas of the Central Highlands during 2017-18. However, there is a low probability of a widespread infestation developing in the Central Highlands, eastern Central West or South Central regions of Queensland during spring or summer.