This page summarises the known distribution of locusts during February and provides a brief outlook for autumn 2015. Regional information and forecasts are given in the latest locust bulletin.
A widespread, high density adult generation developed in several regions of Queensland and New South Wales during February. Swarms formed in parts of South Central, Central West, Northwest and Southwest Queensland, and in Central West New South Wales. Localised nymph bands developed in parts of Far West New South Wales and Far North South Australia in early February, after sporadic swarm egg laying in mid-January. Early instar nymph bands also developed in eastern Central West New South Wales, following swarm egg laying in early February. Swarms persisted in Southwest and Central West Queensland, but densities declined in the South Central region. However, egg laying appears to have been restricted in Queensland, with few laying reports and little egg development in most sampled swarms. Adult numbers remained generally low in other regions of Victoria, South Australia and New South Wales, although a moderate increase was detected in the Riverina and Far Southwest of New South Wales.
In New South Wales, swarms formed in the Warren–Gilgandra–Baradine–Coonamble area of the Central West region in early February. Swarm egg laying occurred in this area in early February, extending into the Coonabarabran district, and localised nymphal bands developed in late February. Bands developed in the Fowlers Gap–Cobham–White Cliffs area in early February and nymphs there began fledging at the end of the month. Adults numbers were at low-medium densities in most regions, but swarms persisted throughout February in the Central West.
High density adults and numerous swarms developed in the Maranoa, Western Downs and Goondiwindi Regional Council areas of South Central Queensland in early February, but densities declined in many areas during the second half of the month. A larger population developed throughout Southwest, Northwest and Central West Queensland, with high adult densities and swarms recorded throughout February. Heavy rainfall was restricted to parts of the South Central and Central West regions during February, limiting the likely extent of an autumn nymphal generation.
A nymphal generation developed in parts of Far North South Australia during February, following swarm egg laying in favourable habitat areas in the second half of January. Swarm egg laying was reported in an area of residual green vegetation between Hawker and Parachilna in early February. Surveys at the end of February identified bands of late instar nymphs on the eastern side of the North Flinders Ranges and medium density nymphs and fledglings in the Dulkaninna and Mungeranie areas.
The autumn outlook is for a gradual decline in adult populations in South Central, Central West, Northwest and Southwest Queensland, with a moderate risk of localised high density nymphs developing in Paroo, Quilpie and Balonne Shires in late March. Localised increases in adult numbers will occur in Far West New South Wales and Far North South Australia as nymphs continue to fledge in early March. Adult numbers should decline in Central West New South Wales, but sporadic high density egg laying could continue into early March. The third nymphal generation in this region will commence fledging in late March, maintaining locally high adult densities. There is a moderate probability of migration from Queensland into New South Wales and South Australia during March, but the risk will decline during autumn. Migrations into southern South Australia, southern New South Wales and northern Victoria from adjacent regions are possible during autumn.
There has been a significant population increase in the Central West and Northwest regions of Queensland as a result of breeding in December and January. Low and medium density nymphs at various development stages were identified at many locations in these regions, as well as widespread Scattered–Numerous density young adults. Consistent Numerous density nymphs and adults were identified in Winton, Boulia, McKinlay, Richmond and Cloncurry Shires, and in Longreach, Barcaldine and Blackall-Tambo Regional Council areas. Adults were recorded at Concentration density at several locations in Central West Queensland in late February. Numerous density adults and nymphs were also identified in northern Barcoo and Diamantina Shires in the Southwest and in Murweh Shire in South Central Queensland. Late February survey of the southern Central Highlands identified only Isolated–Scattered density adults and occasional nymphs. Occasional late instar nymphs and adults were also recorded in Bulloo Shire and near Clifton Hills in the Far North of South Australia.
Areas receiving heavy rainfall in January and February will have maintained suitable conditions for survival of nymphs hatched in November and December and allowed further breeding. The bulk of the current adult population has fledged from summer breeding. Similar populations are also likely in the Queensland Gulf and some regions of the Northern Territory. Adult densities will continue to increase in Queensland during autumn. The autumn adult population will be significantly larger than in the last three years and overwintering swarms are likely to form in parts of Central West and Northwest Queensland.
The population in the Queensland Central Highlands continued to increase during February and swarms developed in the Emerald and Springsure–Buckland Plains areas. Biosecurity Queensland carried out aerial control of 2,000 ha of swarm infestation and landholders have also undertaken ground and aerial control. Surveys in late February identified Numerous–Concentration density adults south of Rolleston in the area where a localised population has been recorded since January and Scattered–Numerous densities in the Emerald–Rolleston area. Medium density adults were recorded in the Roma–Mitchell and Tambo areas in late February, and occasional adults were recorded elsewhere the Maranoa and Blackall-Tambo Regional Council (RC) areas. Biosecurity Qld identified a swarm north of Morven in mid-February. Occasional adults were also identified in the Longreach and Barcaldine RC areas and in Winton Shire.
The continued storm rainfall in the Central Highlands region during February will have favoured further localised breeding, but there were few reports of swarm egg laying. This species is capable of continuous breeding, which can produce regional populations where all lifestages may be present. Adults identified in parts of South Central and Central West Queensland indicate that breeding and localised population increases are also possible in these regions. Gregarisation of this species can occur at local scales, often associated with cropping in eastern Queensland, and can therefore be difficult to detect without intensive surveys. There is a high probability of further localised gregarious population developments and of a continuing infestation in the Central Highlands region during autumn.