Locust Situation 16 October 2014
This page summarises the known distribution of locusts during early October and provides a brief outlook to December 2014.
The next Locust Bulletin will be produced in November 2014.
Australian Plague Locust (Chortoicetes terminifera)
Surveys and reports during the first half of October have shown that the spring nymph population size is larger in several regions than was estimated from information available in September. Nymphs are now widespread in the Far West and Central West regions of New South Wales and part of South Central Queensland. Most have been recorded at medium densities, but many small bands have been identified in some areas. The majority of nymphs were at late instar stage in mid-October, but early and mid-instars were also recorded at many locations. Fledging during the second half of October will result in a significant increase in adult densities in these regions and will continue into November in some areas. Swarm formation will occur in the Far West and possibly parts of the Far Southwest and Central West regions of New South Wales. There will be an increased risk of migrations from Far West New South Wales into adjacent regions in late October and November.
In New South Wales, surveys of the Central West and Northwest regions in early October identified low density adults and nymphs in the Coonamble district. In mid-October Local Land Services staff recorded medium density mid-instar nymphs and some small bands at a number of locations in the Nyngan–Coolabah and Quambone–Carinda areas, following reports by landholders. Surveys of the Far West in early and mid-October identified increasing numbers of nymphs and numerous small bands in the Broken Hill–Tibooburra and White Cliffs–Wilcannia areas. Nymphs were recorded over a range of development stages, with late instars and flegdling adults at numerous locations in mid-October. Consistent low density adults and occasional medium density nymphs were recorded in the Far Southwest and Riverina regions, but some late nymph emergence is possible in the Riverina.
Early October surveys in the South Central and Central Highlands regions of Queensland identified widespread low density adults and medium density nymphs in part of the Maranoa Regional Council area. Surveys by Biosecurity Queensland in mid-October identified nymphs at various development stages and densities, along with some small bands in a restricted area around Roma. Fledging in late October will produce an increase on adult densities, with the possibility of some localised small swarms. Rainfall in the Central West and Central Highlands during September and October has produced suitable conditions for nymphal development and possible locust breeding.
A low density adult population was identified in the Northwest, Northeast and part of the Far North regions of South Australia in late September. No nymphs were detected, although hatchings would have commenced in late August in northern areas and in September in the Northeast.
In Victoria, localised low density adults were reported from the Beechworth area in late September. Hatching of autumn laid eggs will commence in early October and continue throughout the month, with localised medium–high density nymphs possible in the area south of Robinvale.
The outlook for November–December is for an increase in adult population in several regions of New South Wales and Queensland, with swarm formation in Far West and Far Southwest New South Wales. Localised swarms may also develop in parts of Central West New South Wales and South Central Queensland. The seasonal rainfall outlook for drier than average conditions indicates limited opportunities for widespread locust breeding, but the location of any heavy rainfall in November or December will influence the likelihood of a significant summer generation developing.
Spur–throated Locust (Austracris guttulosa)
Surveys during September and October identified a consistent low density adult population in the Southwest, Central West, Central Highlands and South Central regions of Queensland. Isolated–Scattered density adults were identified in Bulloo, Barcoo, Paroo and Murweh Shires, and Longreach, Barcaldine and Blackall-Tambo Regional Council areas. Numerous density adults were recorded at one location near Thargomindah. Occasional Isolated density adults were identified in Far West and Far Southwest New South Wales.
This species commonly forms largely sedentary swarms during winter, often occurring in woodland areas or along rivers. There were no reports of swarms during winter or September. The current dispersed population represents a typical level for this time of year, but the absence of swarms reflects the low population level and late start to the previous breeding cycle. Some migratory redistribution often occurs at the start of the northern wet season and small increases in local numbers could occur in November or December.
The current population of pre-reproductive adults are the offspring from breeding in the 2013-14 wet season. Adults usually commence breeding in the coming wet season in November or December. However, significant rainfall or green crops can initiate breeding as early as October. The heavy rainfall in the Central Highlands and eastern parts of the Central West Queensland in late September and further falls in October could provide conditions for some early low density breeding. The seasonal rainfall outlook issued by the Bureau of Meteorology in September 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.
Migratory Locust (Locusta migratoria)
Surveys during September and early October detected occasional adults in the Queensland Central Highlands. Although at low densities in the Central Highlands, rainfall in mid-August and during the second half of September will provide suitable conditions for further breeding and a population increase is possible during spring. 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 any widespread infestation developing before 2015 remains low.
Map of locust forecasting regions mentioned on this web page
Circles indicate locations of APLC light traps.
Shaded areas indicate potential locust habitat areas.