This page summarises the known distribution of locusts during August and provides a brief outlook for spring 2015. Regional information and forecasts are given in the latest locust bulletin.
The adult locust population declined to low densities in most regions during autumn. Only low numbers were recorded in Queensland and South Australia, and in Far West and Northwest New South Wales in April. Swarm density adults laid eggs in eastern areas of Central West and Northwest New South Wales during March and April. Medium density adults also remained in limited areas of the southern Riverina and Northwest Victoria and are likely to have laid eggs in localised areas. Breeding in other regions is likely to have been at low densities, but some sporadic laying was possible by residual autumn swarms in Central West and South Central Queensland .
In Central West New South Wales, swarm egg laying was reported in the Gilgandra–Baradine–Coonamble and Coonabarabran–Mendooran–Dunedoo areas during March and April. Sporadic swarm egg laying also occurred in the Gunnedah and Narrabri districts of the Northwest Plains. The majority of identified autumn egg beds were in the Coonabarabran and Dubbo districts. Hatchings will commence in mid-September in the Central West. Nymphs reported near Mullaley in early August were low-medium density overwintering mid-instar nymphs that will fledge in September. Adults also persisted in the Deniliquin–Wakool area of the Riverina in mid-April and egg laying there is likely to produce medium and possibly some high density localised nymphs from early October. Some localised high density hatchings are also possible in the Narrabri, Tamworth, Armidale and Barraba districts of the Northwest Plains. Widespread winter rainfall produced suitable habitat conditions for the survival of nymphs in early spring.
Adult densities declined in all regions of Queensland during April. Surveys by APLC and Biosecurity Queensland staff detected only low density adults in the Southwest, Central West and South Central regions. However, residual medium density adults could have laid in higher densities in localised in parts of in the South Central or Central West regions. Hatching of overwintering eggs will have commenced in early September and could produce localised high density nymphs in October.
Adult numbers declined in Far North and Northwest South Australia during April, after dry conditions and some migration in March. Rainfall during April–June in these regions provided suitable vegetation and soil conditions for egg laying by the remaining adults, which could produce some localised medium density nymphs during September. Only occasional low density nymphs are likely to develop in other regions.
Surveys in northern Victoria during late March detected a small population increase following some immigration from New South Wales. However a number of reports were received from the Wimmera and Mallee districts in mid-April and Department of Economic Development staff identified medium density gravid adults at several locations. Egg laying by these adults could produce localised medium density nymphs developing during October.
The spring outlook is for high density nymphs and bands to develop in eastern areas of the Central West New South Wales, in localised areas of the Northwest and southern Riverina regions, and parts of South Central Queensland. Low densities are expected in the other regions. Hatching will commence in late August in southern Queensland, early September in Central West New South Wales and October in Victoria. There is a low risk of widespread regional infestations developing in spring.
There was a significant population increase in the northern half of inland Queensland during 2014-15, from the low levels of recent years. Widespread breeding occurred during December–February following repeated widespread heavy rainfall. Breeding commenced in late November and the widespread heavy rainfall in December and January in Queensland initiated widespread, repeated egg laying in the Central West, Northwest, Queensland Gulf and Central Highlands regions. Only occasional adults were detected in New South Wales and South Australia during. Fledging of nymphs during late summer and autumn produced a consistent medium density population of immature adults in these regions, with high densities recorded in localised areas. Some swarm control in the Central Highlands during autumn.
Adults aggregate in groups during winter and can form roosting swarms in trees along watercourses or in forest. Breeding commences in spring and egg laying is usually occurs after rainfall. The possibility of an early onset of the wet season in Northwest Queensland could initiate breeding in November. Some swarm movement and migrations are possible during spring, but no swarms were reported during August–September. There is a low risk of widespread regional infestations developing during 2015.
Medium and high densities of this species persisted in the Queensland Central Highlands during autumn. Biosecurity Queensland conducted aerial control of swarms covering a total area of 20,000 ha in the Emerald and Clermont areas in early April. Swarms were also reported in Banana Shire in mid-April. Medium density adults and occasional swarms were recorded in the Blackall-Tambo and Maranoa Regional Council areas in autumn. Several swarms were identified in the Blackall–Yalleroi area of Central West Queensland in late March and occasional adults were recorded in the Longreach area.
This species is capable of producing multiple generations and continuous breeding in favourable conditions, although only limited breeding was likely during winter. Rainfall during winter was limited to several light–moderate falls in the southern Central Highlands and natural pastures are mostly dry. Gregarisation can occur at local scales, often associated with cropping in eastern Queensland, and can be difficult to detect without intensive surveys. Landholders are encouraged to report any swarms, egg laying or hatchings. There is a moderate probability of small gregarious populations developing in the Central Highlands region during spring.