Australian plague locust
The Australian plague locust (Chortoicetes terminifera) is a significant agricultural pest. They infest large areas, outbreaks are frequent, and they can produce several generations in a year.
Adult locust populations can migrate to South Australian cropping and pastoral regions in spring and are readily observed as swarms of adult locusts.
Adults migrate in search of green feed, creating a potential threat to emerging crops in autumn as they feed on green plants. Migrating adult locusts are highly mobile and can move quickly between paddocks and districts, readily reinvading treated areas and feeding on established crops and pastures, particularly where local densities are high.
Adult locusts may lay eggs in suitable areas during autumn. These eggs typically enter a winter dormancy with nymphs hatching in spring. Nymphs then aggregate as 'bands' of juvenile hopping locusts on the ground. Juveniles cannot fly but have wing buds that increase in size as they grow – for more information, see growth stages of hopper nymphs.
The last locust outbreak in South Australia occurred in 2022. The state's largest ever outbreak was in 2010.
Current situation
Following the record-breaking rainfall in February 2026, Australian plague locust activity has increased across parts of South Australia, particularly in the eastern Mallee and northern pastoral regions.
Current conditions, including abundant green feed and good soil moisture across pasture and mixed farming landscapes, continue to provide favourable conditions for locusts.
If favourable conditions persist through winter and early spring, there is potential for localised band formation and further population increases during September and October 2026, with unmanaged nymph bands potentially moving into nearby agricultural production areas later in the season.
PIRSA is continuing to work closely with the Australian Plague Locust Commission (APLC) to monitor the current situation in South Australia, determine predicted hatching date, and the likelihood of spring nymph band development.
Surveillance and risk assessment activities are ongoing, particularly in marginal agricultural and near-pastoral regions where locust populations may build and later move into higher-value cropping areas. These activities will help PIRSA inform producers in the Eastern Mallee and Upper and Western Eyre Peninsula cropping regions about:
- expected spring hatchings
- monitoring and potential control options
- support planning.
Locust bulletin
The Australian Plague Locust Commission (APLC) produces a monthly locust bulletin during the seasons of locust activity (spring, summer and autumn).
Read the latest regional summaries below or download the full bulletin from Locust bulletins.
North East pastoral and Flinders
Locusts and conditions
No surveys were conducted in this district in March and April. Surveys conducted in early May identified frequent numerous-density adults in Flinders district and southern part of North East district with no nymphs detected. Surveys conducted in late May identified frequent numerous-density to medium-density-swarm adults in the southern part and frequent numerous-density adults with occasional concentration-density in south-western part of North East district, and frequent numerous-concentration-density adults in Flinders district with some isolated-density adults in the south-western part of this district.
The light-trap at Dulkaninna did not capture any locusts in autumn, but local population buildup observed by the light-trap operator started from mid-February.
Several locust reports of swarming were received from these two districts in late April, indicating some late southward migrations. PIRSA followed up these reports and conducted ground surveys in mid-May when some medium-density adults remained in the Flinders district.
After a very wet February (above average to highest on record rainfall), these two districts received variable amount of rainfall from 60 mm to over 200 mm with heavier rains in the southwest for March, ranging from very much above average to highest on record levels. Flinders district received less than 15 mm of rainfall (average levels) but the northern part of North East district received nil for April. May rainfall totals varied from 10 to 25 mm for North East district and 25 to 60 mm for Flinders district, generally at above average to very much above average levels. Some habitats may remain favourable for locust breeding.
Forecast
Locust breeding is possible under favourable habitat conditions where some eggs may have laid in autumn, and spring nymphs may commence to hatch from these overwintering eggs in Flinders district and the southern part of North East district from mid-September onwards, likely resulting some localised high densities.
There is a moderate-high probability of some significant bands developing in early spring or migrations developing in late spring.
Risks
There is a moderate-high risk of a regional infestation developing in the southern part of these two districts in spring.
RIverland and Murraylands
Locusts and conditions
No surveys were conducted in this district in March and April. Surveys conducted in early May identified consistent isolated to numerous-density adults in Riverland district and the north-eastern part of Murraylands district without any nymphs detected. By mid-May, frequent numerous to medium-density-swarm adults were identified by survey in the eastern part of these two districts, indicating redistribution may have occurred in May after initial immigrations occurred in late April.
Several locust reports were received from these two districts in late April, indicating immigrations from the north and redistribution to the east may have occurred.
These two districts received 40 to 120 mm of rainfall in March, ranging from above average to highest on record. April rainfall totals varied from nearly nil in the northeast to 30 mm in the southwest, generally at average levels over much of these two districts. May rainfall totals varied from 25 mm to 80 mm at average to highest on record levels. Some habitats should remain in favour for locust breeding.
Forecast
Some overwintering eggs may have been laid in favourable habitats in autumn, and spring generation may start to hatch from these eggs from late September onwards, likely resulting some localised high densities.
There is a moderate-high probability of some nymph bands developing in early spring or migrations occurring in late spring.
Risks
There is a moderate-high risk of a regional infestation developing in spring.
Identification
Adults are relatively easy to recognise by the characteristic black spots on forewings and the tip of the hind wing. Back legs have black spots on the thighs and knees and bright red to orange colouring on the hind leg shanks. They are medium-sized locusts, often seen flying in groups or settling in large numbers on vegetation, particularly during warm, calm conditions.
Nymphs (hoppers) are more difficult to identify individually, as they can resemble other native grasshopper species and vary in colour from green to brown depending on their stage and environment.
Australian plague locust hoppers typically form dense, coordinated marching bands that move and feed together. If such bands are observed, they are very likely to be plague locusts. While other grasshopper species may be present in the same areas, they do not form these large, organised bands or exhibit the same migratory behaviour.
Report locust activity
Landholders are encouraged to report locust activity and monitor paddocks regularly throughout winter and spring.
Observations from growers and agronomists are essential to track locust activity across the state.
Landholders are strongly encouraged to report any significant infestations, including:
- adult swarms
- high densities
- hopper bands
- egg-laying activity.
Reports can be made via the Exotic Plant Pest Hotline on 1800 084 881 or using the report plant pest form.
Include key details such as:
- date
- location (GPS if possible)
- life stage (adults or hoppers)
- density and size of the affected area
- brief description of the habitat.
Controlling locust populations
Landholders are responsible for locust control on their properties. PIRSA assists with control where there are large outbreaks (above 100 hectares) in pastoral areas to reduce overall populations.
Landholders and primary producers are advised to watch out for signs of the pest and to factor in locusts as part of their current pest control planning, following normal crop protection and insect control principles.
Spraying adults is generally considered inefficient because adults are highly mobile and will move in and out of paddocks at short notice.
Spraying adults should only be carried out where protecting a specific crop or pasture is necessary.
Locusts should be directly sprayed, using only an Australian Pesticides and Veterinary Medicines Authority (APVMA) registered or permitted insecticide – see Public Chemical Registration Information System Search.
Products are available containing:
- synthetic pyrethroids
- chlorpyrifos
- malathion.
Speak to your local chemical resellers or consultants for more specific chemical recommendations to suit your situation.
Follow insecticide label instructions and withholding periods for harvest and grazing, particularly as crops near maturity. Note that windrowing is also classified as harvest.
The ideal time to treat locusts is when they in the nymph stage, around 2 to 3 weeks old when they aggregate and form into bands.
Bands may be several square metres or larger. Smaller bands can be directly targeted for spraying rather than the whole crop. Controlling bands reduces overall populations.
It is best to spray locusts directly when they are settled, either late in the evening or early in the morning. Warmer daytime conditions (over 20°C) and light winds (less than 11 kilometres per hour) encourages more flight movement.
How locust plagues develop
Large locust populations develop when rain in warmer months provides ideal conditions of green feed to develop and sustain them.
In suitable climatic conditions locust swarms can migrate to South Australia from south-west Queensland and adjacent areas of New South Wales.
They can then develop into localised populations in South Australia’s northern and north-eastern pastoral zones, and go through an entire new life-cycle in these regions. These have the potential to migrate as adult locust swarms up to 500 km.
Locust plague monitoring
When locust populations are likely to cross into another state the commission undertakes:
- surveillance
- threat assessment
- forecasting
- control measures.
You can play an active role in monitoring locust populations by reporting sightings.