Locust situation 6 February 2017
This page summarises the known distribution of locusts during January 2017 and provides a brief outlook to April 2017. Regional information and forecasts are given in the latest locust bulletin.
Australian Plague Locust (Chortoicetes terminifera)
Locust populations remained at medium densities in many regions during January. However, reports at the end of the month indicated a large increase in adult numbers in parts of the Far North and Northwest regions of South Australia. These developed from breeding that started in mid-December in those regions. Mid-instar nymphs were identified at several locations in Far West New South Wales during January, indicative of the development stages of the nymph cohort in northern South Australia. The expected scale of January populations in Southwest and Central West Queensland was not detected by surveys, which identified mostly low density adults and occasional nymphs. The fledging of the December nymphs in Central West New South Wales produced only a small increase in the regional population level and no swarms were reported in the Trangie–Dubbo area, where there had been small bands. Heavy rainfall in northern South Australia and Southwest Queensland in late January has produced favourable habitat for further locust breeding and nymph survival. An autumn generation of nymphs could develop in February and March.
In Central West New South Wales, low density nymphs were identified in the Trangie–Albert area in early January and a small swarm of fledgling adults was recorded near Narromine. Adult numbers subsequently increased to medium densities in parts of the region. Surveys in the Broken Hill–Tibooburra area of the Far West region recorded medium density adults and low–medium density nymphs at numerous locations. Adult numbers increased to medium densities in the Bourke–Brewarrina area in the second half of January, and a single swarm was identified near Bourke. Population levels are expected to have remained low in the Far Southwest and Riverina regions.
In Queensland, mostly low density adults and occasional late instar nymphs were recorded in the Southwest, Central West and South Central regions during January. Medium density adults were identified in parts of Barcoo and Bulloo Shires. Habitat conditions in several regions remain favourable for localised breeding.
In South Australia, flying locusts were reported from the Coober Pedy–Oodnadatta area in late January. Initial surveys confirmed a widespread medium density population of young adults and mid-instar nymphs in the Northwest region. High numbers of locusts were also reported from the Murnpeowie–Moolawatana area of the North Flinders Ranges.
Population levels are expected to have remained low in Victoria. No surveys were conducted and there have been no reports.
The outlook is for increasing adult numbers and further swarm activity in northern South Australia during February after the fledging of nymphs from eggs laid in late December. There is also potential for another significant nymph generation in northern South Australia, and possibly in Southwest Queensland, in late February and March if swarms lay in habitats made favourable by the heavy rainfall at the end of January. There is a moderate risk of some movements to other regions of South Australia or into NSW during February and the likelihood of southward migrations will increase during autumn. Populations are likely to remain at low–medium densities in most other regions during February, although increased adult numbers are possible in Far West NSW. Medium density populations could establish in southern South Australia and NSW, and possibly northern Victoria during autumn, depending on migrations, but there is a low probability of widespread swarm infestations affecting agricultural regions in several states.
Spur–throated Locust (Austracris guttulosa)
There is a widespread medium density population throughout inland Queensland. Surveys over recent months have identified Scattered-Numerous density adults in the Central West, Northwest and Central Highlands, and parts of Southwest and South Central Queensland. Low density nymphs were identified at many locations in the Central West and northern parts of the South Central region during January. The increase in nymph records reflects more widespread egg laying following heavy rainfall in December.
Surveys in January identified consistent Scattered–Numerous density adults in the Longreach, Barcaldine and Blackall-Tambo Regional Council (RC) areas. Present density nymphs at a range of developmental stages were detected throughout Central West Queensland. Scattered–Numerous density adults and occasional nymphs were also recorded in Quilpie, Paroo and Murweh Shires. Isolated–Scattered density adults were recorded elsewhere in Southwest and South Central Queensland, and also in the Far West, Northwest Plains and Central West regions of NSW.
Heavy rainfall in several regions of Queensland during January will allow breeding to continue. Females can lay several pods over the course of summer. Egg development to hatching in this species takes 3–4 weeks and nymph development a further 8–10 weeks. Further nymphs are likely to develop during March and April. Fledging of nymphs hatched in previous months will start in February and the numbers of young adults will increase during autumn. These will largely replace the previous generation as it dies out, although some swarms are likely to form in late autumn. There is a low risk of a large increase in overall population level during 2016–17.
Migratory Locust (Locusta migratoria)
The Queensland Central Highlands region was not surveyed during January and this species was not detected in other regions. However, surveys over recent months identified low numbers of adults in the southern Central Highlands.
Rapid population increases can occur in the Central Highlands, eastern Central West and South Central regions of Queensland. Rainfall during January will produce favourable habitat conditions for continued breeding during the remainder of summer. Small gregarious populations could develop in localised areas of the Central Highlands, but there is a low probability of widespread gregarious populations developing during February or autumn.
Locust Forecasting Regions
Map of forecasting regions with potential locust habitats shaded yellow