This page summarises the known distribution of locusts during September and provides a brief outlook for spring 2015. Regional information and forecasts are given in the latest locust bulletin.
The locust population did not increase markedly in October, despite protracted hatching of nymphs from overwintering eggs in Central West New South Wales and adjacent regions. Nymphs consequently increased in these regions with a range of age cohorts apparent, and developed into localised medium to high density adults. Adult populations generally decreased to sparse but consistent low densities in the arid/semi-arid eastern interior, while medium densities persisted in Central West Queensland.
The southeast section of the eastern Australian locust habitat received moderate to heavy rainfall in the past month. In early October, there was little or no rain over the habitat, and only showers and light storms fell over scattered areas of the southeast in mid-October. Later in October, a surface trough over eastern Australia combined with a cold front crossing Tasmania produced moderate falls scattered across central NSW. A surface trough and low pressure system later developed in eastern Queensland and generated localised moderate storms from central Queensland to central NSW. At the end of October, another surface trough and cold front combination resulted in moderate to localised heavy storms over an area from central NSW extending to the Queensland gulf. The arid interior had light to localised moderate rainfall in early November. The current strong El Niño in the Pacific Ocean is forecast to persist until the end of the year, so warmer and drier conditions are generally expected in southeast Australia.
In Central West NSW and surrounding areas, hatchings were first reported in mid-September and continued to the end of October. The majority of bands were reported from the Dubbo-Gulargambone-Mullaley-Mudgee area, and some from Gunnedah-Narrabri-Moree-Tamworth-Quirindi and Condobolin-Nyngan-Forbes areas. The NSW Local Land Services conducted aerial surveys in mid- and late October and identified a number of bands scattered over a wide area of Central West and adjacent regions. Medium to high density adults were detected in Nyngan-Nymagee-Girilambone and Moree-Narrabri areas from surveys in late October, and such localised high density adults are expected to occur in other parts of this region despite landholder control. Only low-density adults were observed in the Far West and Riverina, and are likely to be present in the Far Southwest. Scattered low to medium density late instar nymphs were found in the Broken Hill area, while first hatchings were seen in the Deniliquin area in late October with more expected elsewhere in the Riverina.
Only localised medium density adults remained in the Tambo area of Central West Queensland, with low density adults found elsewhere. No further nymphs were detected during surveys in early November.
Adult numbers are forecast to have remained low in South Australia. Surveys were only conducted in the northeast corner of the Far North where occasional low density adults detected, but generally low density adults are expected in all regions. This is based on the very limited rainfall in October and only two isolated reports of late instar nymphs from Murray Valley and Southeast in the second half of October.
Low density adults are expected to have remained in northern Victoria, with localised hatchings expected in the coming weeks. Based on adult populations present at the end of autumn, the density and extent of these hatchings is forecast to be limited.
The outlook to January is for localised areas of high density adults in Central West NSW and surrounding areas, with a small chance of population redistribution. Low densities are expected to persist in the other regions of eastern Australia except for the Tambo region, with no significant immediate population build up resulting from recent rainfall. There is a low risk of widespread infestations across regions.
Following a report of high density adults from the Tarcombe area 120 km southwest of Longreach, surveys confirmed Concentration to Low-density-swarm densities present in the area. There were also consistent low-density adults found elsewhere in Central and Western Queensland, and occasionally in New South Wales and South Australia during surveys in mid-October and early November. The annual breeding sequence should be initiated soon after the recent widespread moderate to heavy rainfall in most central and eastern areas of Queensland and central and northeast of New South Wales. Localised hatchings are likely to appear from late November.
There is a low risk of widespread infestations, but a moderate probability of localised medium to high density nymph populations developing in Queensland during 2015.
There were very few migratory locusts detected in the areas surveyed from mid-October to early November, but the low-density adults found from previous surveys are expected to have remained in the Clermont and Springsure areas of the Central Highlands and South Central Queensland regions. The recent widespread moderate to heavy rainfall should encourage reproduction in these areas.
Landholders are encouraged to report any locust activities. There is a moderate probability of small gregarious populations developing in the Central Highlands region.