This page summarises the known distribution of locusts during November 2014 and provides a brief outlook to February 2015.
The next Locust Bulletin will be produced in January 2015.
The locust population remained at widespread medium densities in many regions during November. High densities and some swarms were recorded in limited areas of Far West and Central West New South Wales, and South Central and Central West Queensland during the first half of November. There were significant migratory redistributions throughout the month and in some areas where swarms were previously recorded there were population declines as a result of migrations, dispersal and natural mortality. Increases were detected in parts of Central West and Southwest Queensland in the second half of the month, with swarms recorded in a few localities. No egg laying has been recorded and rainfall was insufficient to initiate widespread breeding until the last week of November.
Large populations were recorded in Far West and Central West New South Wales during the first half of November. Uniform medium density adults and residual late instar nymphs were recorded in habitat areas of the Broken Hill–Tibooburra, White Cliffs–Wilcannia and Bourke areas. A single swarm was identified near White Cliffs. Medium density adults and residual nymphs were also widespread in the northern half of the Central West region and several swarms formed in the Nyngan district. Adult densities are likely to have declined in dry conditions in both regions during the second half of the month. A moderate increase in adult numbers was identified in the Northwest, Far Southwest and Riverina regions.
In Queensland, widespread medium density adults were recorded in the South Central and Central West regions, and in parts of the Southwest and Central Highlands regions during November. Localised high density adults and some swarms were recorded in Murweh and Paroo Shires, and Maranoa Regional Council (RC) area in early November. High densities were identified in parts of Longreach RC area in mid-November and in Diamantina Shire at the end of the month, which are likely to have resulted from immigration. There was a widespread population of Oedaleus australis, up to swarm density in some locations, in the Central Highlands, Central West and South Central regions. Localised storm rainfall occurred several regions during in late November and will produce suitable conditions for aggregation and sporadic swarm egg laying.
In South Australia, adult numbers declined to low densities in areas east of the Flinders Ranges during November. There was a corresponding small increase in numbers in the southern Northeast and Murray Valley regions. Rainfall in these regions during November is unlikely to result in significant locust breeding.
Low density adults and occasional late instar nymphs were identified in Northwest Victoria in late November, representing a small increase in locust numbers.
The outlook for December is for migratory redistribution, aggregation and localised swarm egg laying in areas where moderate–heavy storm rains fell in late November, or occur in early December. The current population distribution indicates this is likely in parts of Southwest, Central West and South Central Queensland, and in Far West and Central West New South Wales. Further storm rains during December and January will influence the likelihood and locations of a significant summer nymphal generation developing and surviving to fledge in January. The seasonal rainfall outlook indicates limited opportunities for widespread locust breeding, but single heavy rainfall events can result in successful breeding and significant population increases. There is a moderate risk of localised high density adult populations developing in several regions during January.
There is a low density adult population throughout inland Queensland. Surveys during November identified Isolated–Scattered density adults in the Central West, Northwest, South Central and Central Highlands regions of Queensland. Occasional adults were identified in Far West New South Wales and Northeast South Australia.
The current adult population is expected to have commenced breeding in northern areas where moderate–heavy rainfall occurred in November. The storm rains in parts of the Queensland Central Highlands, Central West and Gulf regions may initiate egg laying that would produce localised low density nymphs from late December. The distribution of rainfall during the northern wet season will influence the locations, duration and success of the summer–autumn breeding cycle. The current low population level and the seasonal rainfall outlook issued by the Bureau of Meteorology of a low probability of exceeding median rainfall in eastern Queensland supports an assessment of a low risk of a significant infestation developing during 2014-15.
Surveys during November indicated a moderate increase in population level in the Queensland Central Highlands. Low density adults were identified in the Springsure–Rolleston and Arcadia Valley areas. Scattered and Numerous density adults were recorded at some locations. No nymphs were detected. Although the population was still at low densities in the Central Highlands, storm rainfall during late November and in December could provide suitable conditions for localised breeding and a further population increase is possible during summer. Gregarisation can occur at local scales, often associated with cropping in eastern Queensland, and can therefore be difficult to detect without intensive surveys. However, the risk of a widespread infestation developing during summer 2015 remains low.