This page summarises the known distribution of locusts during October 2017 and provides a brief outlook to January 2018. Regional information and forecasts are given in the
latest locust bulletin.
Locust densities identified during September and October are among the lowest spring population levels on record for these months. Surveys recorded very few adults in South Australia, Queensland and New South Wales. Rainfall during winter and September was well below average over most of inland eastern Australia, and habitat conditions remained very dry. However, since the end of September there has been moderate–heavy rainfall in several regions, with some areas recording several significant rain events. Vegetation has responded to these rains and this is likely to initiate low density locust breeding in numerous areas. Large population increases are unlikely during November and December, given the very low background spring population levels.
In New South Wales, survey of the southern Central West and northern Riverina identified only occasional low density adults. No nymphs were detected. Rainfall in the Northwest, Central West and part of the Far West regions may have initiated some low density egg laying.
Survey was conducted in Southwest Queensland in mid-October. Very few adults were identified and no nymphs were detected. Heavy rainfall in the Central Highlands and South Central regions, as well as in Quilpie and Bulloo Shires of the Southwest, is likely to have initiated some low density egg laying.
In South Australia, surveys in late September identified only occasional adult locusts in the Far North, Northwest and Northeast regions. Heavy rainfall in the Oodnadatta area is likely to have initiated some low density egg laying.
There was no survey or report information from Victoria during October. Any spring hatchings will have occurred during the month and the locust population is likely to remain at a low level.
Sporadic hatchings have continued in parts of the of Western Australian wheatbelt. The Department of Primary Industries and Regional Development received reports of mid-instar nymphs from several districts in the Central Agricultural Region.
The outlook for the remainder of 2017 is for population densities to remain generally low in all regions of inland eastern Australia. Breeding in areas that received heavy rainfall during October is likely to produce mostly low density nymphs during November. Fledging of nymphs in December would result in only moderate regional adult population increases. The probability of a summer nymph generation, which could result in significant population increases in January and February, will depend on the distribution of moderate–heavy rainfall during December. Given the current very low population densities, there is a low risk of widespread regional infestations developing during summer. However, seasonal rainfall forecast models suggest an average rainfall expectation over coming months and even isolated heavy rainfall events can result in localised large population increases.
There is a widespread low density population of adults in inland Queensland. Surveys in September and October identified Isolated–Scattered density adults in the Southwest, Central West, South Central and Central Highlands regions. 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. Breeding does not usually commence until the onset of the northern wet season. Rainfall during October, particularly in the Queensland Central Highlands, northern Central West and South Central regions, has created favourable habitat conditions for the commencement of breeding. Eggs take 3–4 weeks to hatch after laying and nymph development, a further 8–10 weeks. Nymphs are likely to appear in those regions from late November. 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 or migrating into agricultural regions during the remainder of spring or summer. The likelihood of an overall population increase during 2017-18 will depend on the frequency and persistence of rainfall during the wet season.
The Queensland Central Highlands and South Central regions were not surveyed during October, but previous survey in September identified occasional low density adults at several locations south of Emerald. Isolated density adults were recorded in the Rolleston and Taroom–Roma areas but no nymphs were detected. 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 during October has 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 November or summer.