Locust situation 4 April 2017
This page summarises the known distribution of locusts during March 2017 and provides a brief outlook for spring 2017. Regional information and forecasts are given in the latest locust bulletin.
Australian Plague Locust (Chortoicetes terminifera)
Locust populations remained at low densities in most regions during March. However, medium density adult populations were maintained in the Far North region of South Australia and in parts of Southwest Queensland, as a result of breeding in late January. Several small swarms were recorded in the North Flinders Ranges area in late March. Few nymphs were recorded during March, indicating only limited egg laying during February. Habitat conditions in these regions are now mostly unsuitable for autumn breeding. There is unlikely to be significant numbers of nymphs in any region during April or May. Heavy rainfall was limited to the eastern regions of New South Wales and Queensland during March. Parts of Central West and Northwest New South Wales and the South Central, Darling Downs and Central Highlands regions of Queensland received heavy storm rainfall in late March. Habitat conditions will remain favourable for autumn breeding in those regions, but current population levels are low. Most eggs laid in autumn will enter diapause dormancy and not hatch until spring.
The locust population remained at low densities in New South Wales during March. Only occasional low density adults were identified in surveyed areas of the Central West and Riverina regions. More consistent Isolated–Scattered density adults were recorded in the Broken Hill–Tibooburra and White Cliffs–Wanaaring areas of the Far West region. No nymphs were detected during surveys and habitat conditions are now generally dry in most regions.
In Queensland, medium density adults were recorded in the Quilpie and Bulloo Shires of the Southwest region in early March. Medium density adults and occasional late instar nymphs were also identified in the Arcadia Valley and Emerald areas of the Central Highlands. Consistent low density adults were identified in the Longreach and Blackall-Tambo areas of the Central West, the Mitchell–Morven–Augathella area of the South Central region and the Taroom area in Banana Shire. Occasional late instar nymphs were detected in the Augathella–Morven area.
In South Australia, medium density adults and occasional late instar nymphs were identified in the Hawker area in early March, with low density adults elsewhere in the Northeast and the Murray Valley region. Surveys at the end of March identified a widespread medium density adult population in the Far North region, extending from Frome Downs to Murnpeowie in the North Flinders Ranges, across to Maree and Oodnadatta. Localised swarm activity was recorded in the Arkaroola area.
Population levels remain low in Victoria. Surveys in early March identified only occasional adults in the Northwest and North Central regions.
The outlook for the remainder of autumn is for locust population densities to remain generally low in most regions of New South Wales and Queensland. Adult numbers are likely to decline to low densities in the Far North, Northeast and Western Agricultural Northwest regions of South Australia during April and May. The probability of migrations within South Australia will decline by May, but some southward movements are possible in April.
Medium density populations could breed in parts of the Northeast and Western Agricultural regions. The majority of eggs laid during April in all regions will be at low densities and will remain in diapause dormancy during winter. There is a low probability of swarm infestations in any state during autumn. Consequently, there is a low risk of widespread nymph infestations developing in agricultural regions during spring.
Spur–throated Locust (Austracris guttulosa)
A widespread medium density population was recorded throughout inland Queensland during February and March, with a relative decline in breeding adult and nymph numbers detected in some regions. There were also widespread, low and medium density nymphs in Central West and Northwest Queensland, and similar populations are likely in to be the Queensland Gulf region. Low density nymphs were recorded in the Southwest and South Central regions.
Surveys in March identified Scattered–Numerous density adults in the Clermont area of the Central Highlands, the Blackall–Barcaldine–Tambo area of the Central West and the Charleville–Augathella area of South Central Queensland. Lower densities of adults were recorded in Banana Shire, areas south of Emerald in the Central Highlands Regional Council (RC area) and the Roma–Mitchell area in Maranoa RC area. Present density nymphs, mostly at late instar stages, were recorded at numerous locations in the Blackall–Tambo and Clermont areas, and occasionally in other parts of these regions.
Isolated–Scattered density adults were recorded in Quilpie and Bulloo Shires of Southwest Queensland and Isolated density adults in the Far West region of NSW and the Far North region of South Australia.
Heavy rainfall was restricted to parts of the Central West, South Central, Central Highlands and Gulf regions of Queensland during March. This will enable remaining nymphs in those areas to survive to fledging. Females can lay several pods over the course of the wet season, but hatchings will decline in April. Egg development to hatching in this species takes 3–4 weeks and nymph development a further 8–10 weeks. Fledging of nymphs hatched in previous months will continue and the numbers of young adults will increase during autumn. These will largely replace the previous generation as it ages and declines, although some swarms of immature adults are likely to form in late autumn. Those adults will not breed before next spring. There is a low risk of a large increase in overall population level during 2016–17.
Migratory Locust (Locusta migratoria)
Low numbers of adults were recorded south of Emerald in the Central Highlands and north of Roma in South Central Queensland in early March. Surveys identified mostly Isolated density adults in the Springsure–Injune, Buckland Plains and Arcadia Valley districts in the Central Highlands Regional Council (RC) area. Isolated–Scattered density adults were identified in the Taroom area of Banana Shire and in the Roma–Mitchell area of Maranoa RC. Numerous density adults were recorded at one location between Roma and Taroom. No nymphs were detected.
Rapid population increases can occur in the Central Highlands, eastern Central West and South Central regions of Queensland. Patchy storm rainfall during each week of March, and heavy rainfall at the end of the month will maintain favourable habitat conditions for continued breeding during autumn. Small gregarious populations could develop in localised areas of the Central Highlands, but there is a low probability of a widespread infestation developing during autumn or spring.
Locust Forecasting Regions
Map of forecasting regions with potential locust habitats shaded yellow