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.
The last locust outbreak in South Australia occurred in 2022. The state's largest ever outbreak was in 2010.
What to expect and report
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.
Any sightings of Australian plague locusts –either swarms in autumn or emerging nymphs and hopper bands in spring – must be reported either to the Exotic Plant Pest Hotline or use the report plant pest form.
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.