Australian plague locust
Encyclopedia
The Australian plague locust (Chortoicetes terminifera) is a native Australian insect in the family Acrididae
and a significant agricultural pest.
Adult Australian plague locusts range in size from 20 to 45 mm in length and the colour varies from brown to green. In profile, the head is higher than the thorax
, and the thorax has an 'X' shaped mark. The legs have a reddish shank and the wings are clear other than for a dark spot on the end.
and the adjoining areas of Queensland
and South Australia
as well as Western Australia
. From these areas, the locusts can expand from time to time to be found in the agricultural areas of South Australia, New South Wales—including the Riverina
— and Victoria
. The locust can be found in a variety of grassland and open wooded habitats across the inland areas of the Australian mainland. Upper level winds may occasionally carry locusts to coastal areas of the mainland and northern Tasmania
and may establish populations in the eastern valleys of the Great Dividing Range
; these populations usually fail to establish themselves for more than a few generations.
Adult locusts— feeding on green shoots that follow rain within 24 to 48 hours in warmer months—will mature and lay eggs within five to seven days of a rain event. Using their ovipositor
to drill a hole, locusts lay their eggs in the soil in a pod. Pods contain around 30 to 50 eggs and locusts lay 2–3 pods, 5 to 10 days apart. Egg laying often happens en masse with as many as a million laid in a hectare of suitable soil. In good conditions (i.e. warm and moist) eggs take around two weeks to develop.
After hatching, the nymphs
take around 20–25 days to complete development in mid-summer. The locust has five instar
s, with the wings becoming more prominent with each moult. After the first and second instar, nymphs will form aggregations known as bands; these tend to disburse by the fifth instar. Late instar bands will travel up to 500 metres per day. Drier country will see large bands congregate that are visible from the air while in the agricultural regions, bands will tend to be smaller.
After its final moult—6 to 8 weeks after egg laying—the adult locust is called a fledgling. Fledglings have three development stages; a growth phase, where wings are strengthened and the exoskeleton
hardened, a fat accumulation stage and lastly, oocyte
development. Gregarious populations of locusts will form swarm
s, recurring in central Eastern Australia once every two or three years. The Australian plague locust is less gregarious than other locust species and swarms occur in a continuum from dense swarms through a range of densities down to scattered adults. Swarms may persist for days; dispersing and reforming while following the wind. Swarms may move up to 20 kilometres in a day. Swarms can infest areas up to 50 square kilometres (19.3 sq mi), although typical infestations are less than 5 square kilometres (1.9 sq mi). Swarms can travel up to 800 kilometres (497.1 mi) tending to move with hot winds and generally towards the coast in most cases.
Infestations in Western Australia are less frequent. Widespread heavy inland rains, especially in summer, will allow plague locusts to reach plague proportions with less regular rain maintaining these high density populations. During these condition the life-cycle pattern may change to one in which the period from hatching to maturity is reduced to two and a half months. Dry conditions will reduce populations back to background levels.
Due to its large range and frequent plagues, the Australian plague locust is the most damaging locust species in Australia. Damage is mainly confined to pasture
although crop damage can occur. Advanced winter crops have generally hardened off by early summer, when plague locusts become active and therefore are not favoured but dry conditions and less advanced crops can be highly susceptible to locust infestation as can young autumn crops.
Losses in a plague can amount to $3-4 million if protection barriers are ineffective. The Australian Plague Locust Commission
is responsible for the monitoring and control of locust outbreaks using the control agent fipronil
and growth regulators such as diflubenzuron
in the juvenile nymphal stage. Two older-generation organochlorines, fenitrothion
and chlorpyrifos
, are also used occasionally for auxiliary, blanket spray runs, and the bioinsecticide 'Green Guard', made from a native fungal isolate of Metarhizium acridum
. The latter is based on technology developed by CSIRO and the LUBILOSA
Programme and now accounts for >12% of spray applications: for protected, organic farming, or environmentally susceptible areas such as water courses.
Acrididae
The Acrididae are the predominant family of grasshoppers, comprising some 10,000 of the 11,000 species of the entire suborder Caelifera. The Acrididae are best known because all locusts are of the Acrididae. The subfamily Oedipodinae is sometimes classified as a distinct family Oedipodidae in the...
and a significant agricultural pest.
Adult Australian plague locusts range in size from 20 to 45 mm in length and the colour varies from brown to green. In profile, the head is higher than the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
, and the thorax has an 'X' shaped mark. The legs have a reddish shank and the wings are clear other than for a dark spot on the end.
Range and habitat
The locusts occur naturally in far north-western New South WalesNew South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
and the adjoining areas of Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
and South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
as well as Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
. From these areas, the locusts can expand from time to time to be found in the agricultural areas of South Australia, New South Wales—including the Riverina
Riverina
The Riverina is an agricultural region of south-western New South Wales , Australia. The Riverina is distinguished from other Australian regions by the combination of flat plains, warm to hot climate and an ample supply of water for irrigation. This combination has allowed the Riverina to develop...
— and Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
. The locust can be found in a variety of grassland and open wooded habitats across the inland areas of the Australian mainland. Upper level winds may occasionally carry locusts to coastal areas of the mainland and northern Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
and may establish populations in the eastern valleys of the Great Dividing Range
Great Dividing Range
The Great Dividing Range, or the Eastern Highlands, is Australia's most substantial mountain range and the third longest in the world. The range stretches more than 3,500 km from Dauan Island off the northeastern tip of Queensland, running the entire length of the eastern coastline through...
; these populations usually fail to establish themselves for more than a few generations.
Life-cycle
Ovipositor
The ovipositor is an organ used by some animals for oviposition, i.e., the laying of eggs. It consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and to place it properly...
to drill a hole, locusts lay their eggs in the soil in a pod. Pods contain around 30 to 50 eggs and locusts lay 2–3 pods, 5 to 10 days apart. Egg laying often happens en masse with as many as a million laid in a hectare of suitable soil. In good conditions (i.e. warm and moist) eggs take around two weeks to develop.
After hatching, the nymphs
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
take around 20–25 days to complete development in mid-summer. The locust has five instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s, with the wings becoming more prominent with each moult. After the first and second instar, nymphs will form aggregations known as bands; these tend to disburse by the fifth instar. Late instar bands will travel up to 500 metres per day. Drier country will see large bands congregate that are visible from the air while in the agricultural regions, bands will tend to be smaller.
After its final moult—6 to 8 weeks after egg laying—the adult locust is called a fledgling. Fledglings have three development stages; a growth phase, where wings are strengthened and the exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
hardened, a fat accumulation stage and lastly, oocyte
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
development. Gregarious populations of locusts will form swarm
Swarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by animals of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. As a term, swarming is applied particularly to insects, but can also be applied to...
s, recurring in central Eastern Australia once every two or three years. The Australian plague locust is less gregarious than other locust species and swarms occur in a continuum from dense swarms through a range of densities down to scattered adults. Swarms may persist for days; dispersing and reforming while following the wind. Swarms may move up to 20 kilometres in a day. Swarms can infest areas up to 50 square kilometres (19.3 sq mi), although typical infestations are less than 5 square kilometres (1.9 sq mi). Swarms can travel up to 800 kilometres (497.1 mi) tending to move with hot winds and generally towards the coast in most cases.
Plagues
When food and climatic conditions are favourable huge swarms of locusts may develop. The first recorded swarm was in 1844, with further outbreaks from the 1870s onward. After 1900, the intensity and frequency of locust swarms increased and since the 1920s, a pattern has developed of localised high density populations in some locations most years and less frequent major plagues over large areas persisting for one to two years.Infestations in Western Australia are less frequent. Widespread heavy inland rains, especially in summer, will allow plague locusts to reach plague proportions with less regular rain maintaining these high density populations. During these condition the life-cycle pattern may change to one in which the period from hatching to maturity is reduced to two and a half months. Dry conditions will reduce populations back to background levels.
Due to its large range and frequent plagues, the Australian plague locust is the most damaging locust species in Australia. Damage is mainly confined to pasture
Pasture
Pasture is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep or swine. The vegetation of tended pasture, forage, consists mainly of grasses, with an interspersion of legumes and other forbs...
although crop damage can occur. Advanced winter crops have generally hardened off by early summer, when plague locusts become active and therefore are not favoured but dry conditions and less advanced crops can be highly susceptible to locust infestation as can young autumn crops.
Losses in a plague can amount to $3-4 million if protection barriers are ineffective. The Australian Plague Locust Commission
Australian Plague Locust Commission
The Australian Plague Locust Commission is a division of the Australian Department of Agriculture, Fisheries and Forestry, created in 1974 to manage outbreaks of the Australian plague locust, spur-throated locust and migratory locust in eastern Australia...
is responsible for the monitoring and control of locust outbreaks using the control agent fipronil
Fipronil
Fipronil is a broad spectrum insecticide that disrupts the insect central nervous system by blocking the passage of chloride ions through the GABA receptor and glutamate-gated chloride channels, components of the central nervous system. This causes hyperexcitation of contaminated insects' nerves...
and growth regulators such as diflubenzuron
Diflubenzuron
Diflubenzuron is an insecticide of the benzamide class. It is used in forest management and on field crops to selectively control insect pests, particularly forest tent caterpillar moths, boll weevils, gypsy moths, and other types of moths. The mechanism of action of diflubenzuron involves...
in the juvenile nymphal stage. Two older-generation organochlorines, fenitrothion
Fenitrothion
Fenitrothion is a phosphorothioate insecticide....
and chlorpyrifos
Chlorpyrifos
Chlorpyrifos is a crystalline organophosphate insecticide that inhibits acetylcholinesterase and is used to control insect pests. It is known by many trade names...
, are also used occasionally for auxiliary, blanket spray runs, and the bioinsecticide 'Green Guard', made from a native fungal isolate of Metarhizium acridum
Metarhizium acridum
Metarhizium acridum is the new name given to a group of fungal isolates that are known to be virulent and specific to Acrididea. Previously, this species has had variety status in Metarhizium anisopliae and before that, reference was made to M. flavoviride.- Biology :M...
. The latter is based on technology developed by CSIRO and the LUBILOSA
LUBILOSA
LUBILOSA was the name of a research programme that aimed at developing a biological alternative to the chemical control of locusts. This name is an acronym of the French title of the programme: Lutte Biologique contre les Locustes et les Sauteriaux...
Programme and now accounts for >12% of spray applications: for protected, organic farming, or environmentally susceptible areas such as water courses.
See also
- Agriculture in AustraliaAgriculture in AustraliaAustralia is a major agricultural producer and exporter. Agriculture and its closely related sectors earn $155 billion-a-year for a 12% share of GDP. Australian farmers and graziers own 135,996 farms, covering 61% of Australia’s landmass. There is a mix of irrigation and dry-land farming...
- APLC
- LUBILOSALUBILOSALUBILOSA was the name of a research programme that aimed at developing a biological alternative to the chemical control of locusts. This name is an acronym of the French title of the programme: Lutte Biologique contre les Locustes et les Sauteriaux...
- Spur-throated locustSpur-throated locustThe Spur-throated locust is a native Australian insect in the family Acrididae and a significant agricultural pest.Adult females of A. guttulosa are typically long, and adult males are typically long.-See also:...
, Austracris guttalosa - another plague locust in Australia
External links
- Department of Agriculture Forestry and Fisheries information page on plague locusts
- Save the Locust - information on learning to live with locusts