Current Locust Situation and News

Locust situation January 2012

This page summarises the known distribution of locusts during December 2011 and provides a brief outlook to February 2012. The next Locust Bulletin will be produced in February 2012.

• Australian Plague Locust situation  
• Spur–throated Locust situation 
• Migratory Locust situation
• Map of forecasting regions

Australian Plague Locust (Chortoicetes terminifera)

Population density remained low throughout western Queensland and New South Wales, and in northern South Australia and Victoria during December. An area of high density adults and swarms formed in part of the Northeast region of South Australia and some swarm egg laying is likely to have occurred during the second half of December. There were very few reports of locust activity in Victoria and southern South Australia, indicating a decline in population level. Surveys indicated continued low background population levels in the Far West, Far Northwest, Central West and Riverina regions of New South Wales, and in Southwest and Central West Queensland.

The outlook is for a decline in adult densities in the infested area in Northeast South Australia during January, with the likelihood of a summer generation of nymphs in localised areas and the possibility of some hopper band activity. The congregation and development of initially small, gregarious high density populations is possible during summer in parts of Southwest Queensland, Far West New South Wales or the Far North of South Australia. This usually occurs in response to heavy, early summer rains which can initiate a summer breeding cycle. However, no higher density adult populations have developed in these regions at this stage and the probability that any which may appear in late summer will present a migration risk and serious threat in agricultural areas during autumn has consequently declined. The population level is expected to remain low in Victoria.

In South Australia, high density adults and a number of swarms were identified in the Peterborough–Burra–Spalding–Jamestown area during December. There were also low density late instar nymphs in some locations. Samples from swarms indicated that egg laying was likely to occur during the second half of December. Heavy rainfall in that part of the Northeast in mid-December will produce suitable conditions for a high rate of nymphal survival. Nymphs are likely to appear in mid-January and would fledge during the second half of February. The background population in the Northwest and Far North region may have been maintained by migration from the Northeast region during December.

Surveys in New South Wales showed a continuing low density population in all regions during December. Adult numbers remained very low in the Central West, Darling and Riverina Livestock Health and Pest Authority (LHPA) areas, while some scattered adults were identified in part of Western LHPA. The development of localised medium density populations is possible in parts of these LHPA areas in late summer, which could produce local autumn nymphal populations, although if this occurs it is unlikely to present a widespread threat to agriculture.

Surveys in Southwest Queensland identified a low density adult population in some areas and very few nymphs. Heavy rainfall in Quilpie and Barcoo Shires during December will produce suitable habitat conditions for locust breeding and nymphal survival. A summer generation of nymphs in some locations is possible during January.

The absence of any areas of higher density adults in Victoria is an indication of the continuing decline in population level. There is a low risk of any significant population development during summer or autumn, or of significant immigration from other states.    

6 January 2012 

•  Spur–throated Locust (Austracris guttulosa)
  

There is a widespread low density population of adults throughout the inland regions of New South Wales, Queensland and South Australia. Adults appear to have dispersed across most regions and are likely to have commenced breeding in several regions of Queensland and northern New South Wales during December. Early instar nymphs were detected in the southern Central Highlands of Queensland. There is a low probability of swarms appearing in agricultural regions of Queensland or northern New South Wales during summer.

Surveys in Queensland during November and December identified consistent Isolated-Scattered density adults throughout the Northwest, Southwest, Central West, South Central and Central Highlands regions. Densities were highest in the Longreach–Muttaburra and Dirranbandi–Hebel areas, where there were several Numerous density counts. Low density early instar nymphs were recorded in the Rolleston area of the Central Highlands in mid-November, but no nymphs have been detected in other regions. In New South Wales there were consistent Isolated-Scattered density adults in the Darling, Northwest Plains and Central West LHPA areas, and Numerous density adults in the Walgett–Goodooga area.  Adult densities were lower in Western and Riverina LHPA areas, and across northern South Australia, where consistent Isolated density adults were identified.

The outlook is for low density egg laying to continue in parts of the Central Highlands, South Central, Central West, Northwest and Queensland Gulf regions of Queensland during summer. Some low density laying is also likely in the Darling and Northwest Plains LHPA areas of northern New South Wales. This species does not lay in dense egg beds and nymphs are generally not gregarious. Adults can lay multiple egg pods and nymphs are likely to occur across several development stages during summer.      

Migratory Locust (Locusta migratoria)

APLC surveys did not detect this species during December, but in November identified occasional Isolated density adults were identified in the Warialda area of the Northwest LHPA and in the Clermont–Gregory area of the Queensland Central Highlands. Low numbers of this species commonly occur in these regions during summer. It is capable of continuous breeding over several generations in Queensland and northern New South Wales. The heavy rainfall which has continued from October to December in South Central Queensland and the NSW Northwest Plains, could have allowed successful breeding of the low density population. There is the potential for the development of localised small gregarious populations of this species during summer, although the probability of a significant infestation remains low.

Map of locust forecasting regions mentioned on this web page

Circles indicate locations of APLC light traps.