This page summarises the known distribution of locusts during November 2017 and provides a brief outlook to February 2018. Regional information and forecasts are given in the
latest locust bulletin.
Locust densities remained low in all surveyed regions during November. Despite rainfall producing more favourable habitat conditions in many areas, only low density adults and very few nymphs were identified during surveys. Locust numbers remained low in the Central West, Northwest Plains, Riverina and Far Southwest of New South Wales, South Central and Southwest Queensland, and in the Far North, Northeast and Northwest regions of South Australia. Some low density egg laying is likely to have occurred during late October and November, so moderate increases in population from a very low base level are likely during December and January.
In New South Wales, survey of the Central West and Northwest Plains recorded low density adults and only occasional nymphs. Survey of the Far Southwest and Riverina regions in late November identified low density adults in most areas, but localised medium density young adults and occasional nymphs were recorded in the Ivanhoe district.
Surveys in Southwest, Central West and Northwest Queensland identified very few adults and no nymphs were detected. Survey in South Central Queensland in mid-November identified more consistent low density adults.
In South Australia, surveys in mid-November identified only occasional adult locusts in the Far North, Northwest and Northeast regions.
Survey of Northwest Victoria in late November identified low density adults.
In Western Australia, fledging of spring generation nymphs produced medium density adults in several areas of the Central Agricultural Region.
The outlook for summer is for population densities to remain generally low in all regions of inland eastern Australia. Localised breeding is likely to occur in habitat areas that receive heavy rainfall in December and this will result in small regional population increases. Breeding is likely to continue during summer and autumn, but given the current very low population densities there is a low risk of widespread regional infestations developing during summer, and a very low risk of swarms affecting agricultural regions across several states in autumn. The probability of a late summer or autumn nymph generation, which could result in localised dense infestations, will depend on the development of nymphs during December. Seasonal rainfall forecast models suggest an average rainfall expectation over coming months and a sequence of rainfall events during summer could result in significant population increases in autumn.
There is a widespread low density population of adults in inland Queensland, with medium densities in Northwest and Central West regions. Surveys in November identified consistent Isolated–Scattered density adults in Southwest and South Central Queensland. Scattered–Numerous density adults were identified in the Richmond, McKinlay and Flinders Shires. Samples showed females were developing eggs. Occasional adults were recorded in the Far North and Northwest regions of South Australia and in Far West New South Wales.
Migrations and local swarm movements of over-wintered adults often occur during spring and early summer. The Central Highlands has not been surveyed since September, when only low density adults were recorded, and adult densities are likely to have increased as a result of redistribution and aggregation. Rainfall in recent months, particularly in the Queensland Central West, Central Highlands and South Central regions, created favourable habitat conditions for the commencement of breeding. Nymphs are likely to develop in several regions of Queensland during December. Females can lay multiple times during summer, usually following significant rainfall. Nymphs of this species do not usually aggregate to form cohesive bands, but can reach densities of 30/m2 in favourable habitats.
There is a low risk of swarms developing in or migrating to agricultural regions during summer. The likelihood of an overall population increase during 2017-18 will depend on the frequency and persistence of rainfall during the northern wet season.
Low numbers of this species were identified at one location near Taroom in South Central Queensland during November. Previous surveys in the Central Highlands identified low number of adults at several locations south of Emerald. Populations of this species are commonly found in these regions and rapid population increases are possible in favourable habitat. Gregarious populations can occur at local scales and are often associated with forage or cereal cropping.
The heavy rainfall in the Central Highlands and South Central regions of Queensland over recent months produced suitable soil and vegetation conditions for breeding. Small gregarious populations could develop in localised areas of these regions during 2017-18. However, there is currently a low risk of a widespread infestation developing during summer.