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Plague Locusts - Frequently Asked Questions
General | New South Wales | Advice to Farmers | Government Action | Possible Spread | Information
General
What is an Australian Plague Locust?
An Australian Plague Locust is a type of insect similar to grasshoppers, katydids and crickets - the Orthoptera (derived from the Greek words orthos meaning straight or rigid and ptera meaning wing).
The major difference between grasshoppers and locusts is the capability of immature locusts (hoppers) to form dense aggregations called bands and of adult locusts to form swarms. Bands and swarms generally form when the population density is high.
Grasshoppers do not form bands or swarms.
Another key difference between locusts and grasshoppers is that locusts have a large dark spot on the tip of the rear wings and a distinctive red line on the rear legs.
The Australian Plague Locust is a native species that occurs naturally in the far north west of New South Wales and adjacent areas of Queensland and South Australia. It is one of many locust species.
Why are locusts pests?
The ability of locusts to form into dense aggregations as hoppers (bands) or adults (swarms) make them formidable eating machines that can rapidly devastate crops. The highly mobile nature of swarms and their ability to migrate over large distances means that virtually all agricultural areas are at risk of damage.
When was the last time we had a locust plague in Victoria?
The last locust plague occurred during 2005-06.
What happened then?
Unusually large swarms of locusts developed following an extreme rainfall event in Queensland in 2004. The swarms and subsequent generations moved south through NSW and finally to Victoria in autumn 2004.
The ‘incursion event’ led to significant hatchings of locusts in Victoria during the spring, summer and autumn of 2005 and 2006. In 2005, outbreaks occurred near Mitiamo in north central Victoria and Swifts Creek in southern Victoria.
In autumn 2008 a significant migration of locusts from NSW - that are believed to have originated in QLD – moved into northern Victoria.
Egg bearing locusts were also observed over a large area however these eggs did not begin hatching until the following Spring in 2008. The immature locusts (hoppers) that emerged from these eggs were mostly found in the irrigated area north of Shepparton.
Control operations were successfully directed against these hatching hoppers, however due to the number of infested sites some locusts survived through to adulthood in early summer – December 2008.
More numerous and larger swarms of adult locusts developed in NSW and some of these swarms managed to cross the Murray River and enter Victoria, especially near Echuca and Yarrawonga. This summer flight of locusts boosted the relatively smaller numbers that were already present in Victoria and large numbers of eggs were laid at some sites close to the points where they had crossed into the State. These eggs hatched in January 2009.
That generation of hoppers matured and took flight from mid-February 2009 and began laying another generation of eggs during March to April 2009. However there was little evidence of extensive egg laying. These eggs are likely to hatch in October 2009 but the likelihood of significant numbers of locusts is low.
Why is the full extent of their egg-laying unclear?
Egg-beds are difficult to detect unless female locusts are observed during egg-laying. The full extent of egg-laying does not become apparent until the eggs begin hatching and the hoppers, which are more easily detected, emerge and become active.
What is an egg-bed – and how do I recognise it?
Locusts usually lay eggs on bare damp ground. Female locusts may crowd together and lay large numbers of eggs in a patch of soil suitable for egg-laying. These areas are referred to as ‘egg-beds’ and the eggs are buried below the soil surface.
Locust egg-beds are most easily detected while the locusts are laying eggs. While female locusts are laying eggs and have their abdomen poked into the soil they do not disturb and fly away as rapidly as normal. If egg-laying is not observed it is difficult to know the location of egg-beds prior to eggs hatching.
The ground where locust eggs have been laid looks like a sieve with lots of shallow holes that are very close together. Female locusts will often make test drill holes in the soil without laying any eggs. When looking for egg-beds, care needs to be taken to ensure that sites where locusts have been test drilling are not mistaken as egg-beds and the actual extent of egg-laying is then over-estimated.
People trying to identify locust egg-beds should peg out the affected area for easy future identification and then dig up clods of soil where locusts are seen drilling, or where holes are evident, and then directly inspect the actual density of locust eggs in the soil. Within the short period after egg-laying, the holes created during laying may fill with loose dirt from the surface very quickly removing all traces of egg-laying within as little as two to three hours after the event.
Are eggs always laid in egg-beds?
No. When the adults are in low density, and in some other situations, egg-laying may be scattered across an area.
How many eggs does a female locust lay?
Each female lays pods of 30 eggs sometimes laying only one pod per life time, but up to five pods can be laid. Pods are laid at 5 to 7 day intervals.
What causes locusts to hatch?
Locust eggs only develop in warm moist conditions. Given sufficient moisture and a daily maximum of 35°C, egg development takes just over two weeks, while with a daily maximum of 25°C, it takes over a month. Egg development does not take place below about 15°C.
When will locusts hatch?
Any hatching this spring would be likely to occur in October 2009.
What happens when locusts hatch?
From each egg, an immature locust emerges, called a nymph or more commonly a hopper. As the hoppers grow and develop, they pass through five, and in some circumstances six, stages of development called instars. The hoppers moult between each instar to enable their body to expand. In mid summer, the hoppers take around 20-25 days to complete their development before maturing into adults that are capable of flight.
Australian plague locusts may disperse by walking while young hoppers or by flying as adults. At higher densities, the hoppers may form dense groups known as bands that move across an infested area en masse stripping vegetation. Similarly, adult locusts can form large groups called swarms that can invade and swiftly defoliate plants and crops.
Where will they spread?
Flight is the main method by which locusts spread over large distances. This occurs to a limited extent during the day and more commonly, over much larger distances at night. The extent of migration will depend on a number of factors such as the availability of food, density of locusts and weather conditions. The direction of spread, especially night time long distance migration, depends on prevailing wind directions. The extent of spread is determined by the strength and duration of the wind. It is possible for locusts to travel up to several hundred kilometres per night.
How is a locust different to the common grasshopper?
To the untrained eye it can be difficult to distinguish the Australian Plague Locust from the wingless grasshopper and other locust and grasshopper species.
Adults of the Australian plague locust are distinguished from other species by the large dark spot on the tip of the hind wings and distinctive red line on the hind legs. The hind wings are clear with no other colouration or marking apart from the translucent black area at the tip of the wing.
Also, young locusts are known to form dense groups called ‘bands’ when foraging for food. Similarly, adults form swarms that can migrate great distances overnight.
Conversely, grasshoppers do not have those physical features or form bands and swarms.
What do they eat?
Most species of locust feed mainly on grasses. Locusts in particular prefer to feed on grasses and cereal crops such as wheat. However, when there is little green grass or wheat available they will eat a wide range of plants including: horticulture crops, pasture, grapevines and trees.
How much do they eat in a day?
An Australian Plague Locust eats approximately one third to one half of its body weight per day throughout its life. If a medium or high-density swarm landed on a pasture, a lawn, a golf course, a park, or a similarly grassed area all the grass is likely to be eaten within a few hours.
Do they eat everything in their path?
Locusts, when in plague proportions, are often depicted as ravaging vast areas of countryside and eating everything in their path. However, devastation on such a large scale and intensity is extremely rare.
Likewise, bands of hoppers can do extensive damage to pasture and young cereal crops in spring but as the locusts cannot fly at this stage, damage is limited to the immediate area. Swarms of adult locusts are highly mobile and they will often do severe damage to part of a crop (particularly along the edge) before moving on elsewhere.
The behaviour of a swarm is highly unpredictable and a swarm will sometimes fly over apparently suitable crops. Damage to crops is often worse when conditions are very dry and they eat the only green vegetation remaining. When there is an abundance of green grass, the threat of damage to crops is often reduced.
Do locusts pose a health threat?
Locusts can pose an indirect threat to human health by destroying crops intended for human consumption. In some countries, locusts are themselves used as a food by humans.
New South Wales
Where did they lay eggs in NSW last season?
A heavy nymph infestation is anticipated in west central NSW in Spring 2009.
If they spread south, what will that mean for Victoria?
If the populations develops in NSW it could spread south. However the probability of migration further south than the Riverina area of NSW early in the season is low. It is difficult to gauge the impact of any migration by adult locusts from NSW or possibly Queensland into Victoria during late spring 2009 or summer 2010.
Small scale migration would probably only have a limited effect unless locust activity is concentrated into a small area in Victoria putting localised crops at risk.
Advice to Farmers
Who is responsible for controlling locusts?
In Victoria, the responsibility for controlling locusts on private property rests with the landholder.
What is the most effective way of controlling locusts?
The most effective method of controlling locusts is to target the immature locusts or hoppers with chemical control agents, especially when they occur in groups called ‘bands’.
Will ploughing fields have an impact?
Ploughing paddocks infested with locust eggs may destroy some eggs but usually will not have a significant influence on the overall number of locusts from the infested area.
What are we asking farmers to do?
Effective locust response requires a co-ordinated and carefully targeted control program.
Farmers have a vital role to play by monitoring and promptly providing accurate reports of locust infestations on their property to the DPI; especially where bands of hoppers are observed. In particular, it is important that farmers take responsibility for controlling locusts on their land to ensure that damage to their crops is prevented or minimised and that infestations are prevented from spreading and increasing in size. Contact the DPI: 1300 13 5559.
It is also important to allow The DPI staff access to privately owned land where required to facilitate monitoring.
What can farmers do now?
Landholders are encouraged to peg out any locust infested areas for easy future identification. The DPI is urging landholders to continually monitor the affected areas for signs of locusts laying eggs.
Landholders are more able to control locusts during their early life stages by using one of the several chemicals registered for use in the specific control of locusts.
If you are going to spray your property let you neighbours know. Spraying may have an impact on beehives, so please alert beekeepers in the area.
Contact the Locust Hotline on 1300 13 5559 to report locust activity on your property.
Government Action
What is the DPI’s policy on the use of control agents?
The DPI Locust Management Plan outlines the DPI’s policies in relation to Plague Locusts. The Plan provides guidelines for responding to potential or actual incursions of locusts within Victoria including what control agents will be used, how they will be applied and by whom.
The DPI’s policy on control is:
1. The primary target will be immature locusts (hoppers) with highest priority being treating bands of hoppers, especially when they are located in areas with plenty of green feed and more likely to complete their development and become adults that can swarm. Roadsides would also be treated where bands are likely to move from adjacent areas and when other control options are not possible.
2. Hoppers on private or public land (including roadsides and railway reserves), may also be treated where the density is too low to form bands, but high enough over an extensive area to mature into adults and move to other areas.
3. Private or public land will only be treated after permission has been sought and gained from relevant land owner/manager.
4. Choice of control agent will depend on the sensitivity of the area being treated and the availability and suitability of control agents and application equipment; together with the consent of landowner and applicator.
5. The DPI will consider the requirement for action against a generation of locusts based on an extensive monitoring program.
6. There will be no control activities against adult locusts.
7. The DPI will not issue control agents to landholders
Will the Government provide control agents?
The State Government will purchase control agents for use solely by DPI staff or for aerial and ground applicators operating under contract and supervision of DPI staff operating in accordance with the Locust Management Plan.
Will the Government spray locusts?
The DPI will undertake targetted control of locust hoppers only in specific circumstances on public or private land to reduce the locust population and minimise dispersal of adult locusts.
How will spraying programs be conducted?
The control agents are applied either aerially or with ground-based equipment. The choice of the method of application will be determined by the location of the area to be treated and the suitability of this area for treatment by either application method. For example, in areas where there are large numbers of trees, dwellings or where only a small area requires treatment, ground application will be feasible. The choice of the application will follow guidelines and policy described under the Locust Management Plan (version 6.0).
Which control agents will the DPI use?
The current version of the response plan lists control agents that contain the following active ingredients:
1. Metarhizium, a fungus which attacks and kills locusts over a period of 10 – 30 days.
2. Fipronil, a residual (15- 20 days) chemical that can be used to produce a barrier that kills locusts if they move across the treated area.
3. Fenitrothion is a chemical used extensively by the Australian Plague Locust Commission and has a 2-3 day active period.
Are the control agents dangerous?
The DPI will only use registered control agents in accordance with the labels and will observe all directions.
People handling and applying the control agents must use appropriate protective gear. No-one should enter sprayed areas before the withholding period has passed.
The control agents must be applied only in places and by methods that minimise the risks including: insecticide drifting into areas that should not be treated.
How will the DPI minimise the risks when it sprays?
In all its handling of control agents, the DPI will strictly comply with all safety requirements.
In selecting areas to be sprayed, the DPI will strictly adhere to the buffer zones that have been developed and proven over many years by the Australian Plague Locust Commission. These buffers ensure that there will be no drift of insecticide into sensitive areas, such as: crops, animals, schools water bodies and residential areas that should not be sprayed.
Will they damage plants or animals?
Damage to plants and animals can be avoided when control agents are used in accordance with the pesticide label recommendations, such as: adhering to withholding periods; crop safety recommendations; rates and methods of application; and only allowing trained & certified people to apply the control agents.
Possible spread
What will happen if locusts spread to Melbourne and major regional centres?
If locusts do manage to reach Melbourne, they are likely to occur as individual adults locusts during the day or more likely as swarms migrating long distances overnight.
What action should motorists take?
Locust swarms can significantly reduce a driver’s ability to see the road and oncoming traffic. Driving through locust swarms can also block radiators, causing a vehicle to overheat. Consequently, the DPI and RACV developed some tips for motorists so they know what they should do:
- before they depart on holiday, and
- what to do if encountering a swarm Australian Plague Locust while driving
Before you leave home:
- Add some specially formulated insect cleaning agent to the windscreen washer system (available at supermarkets, auto accessory outlets and service stations.)
- Consider attaching an insect screen on your external radiator air-inlet for extra protection
- Pack a bag with spare water and extra insect cleaning agent and cloths/rags
- Check this website for the latest Australian Plague Locusts update or call the Locust Hotline: 1300 13 5559
Driving through a swarm of Australian plague locusts:
1. If visibility is somewhat impaired due to locust swarms
- Slow down – gradually reduce your speed and continue driving carefully
- Turn on your headlights – to alert oncoming traffic of your presence
- Be aware that traffic coming from the opposite direction will also have reduced visibility
- Use your windscreen wipers to clear locusts from your windscreen - well-fed locusts leave a residue of body parts and fat at the point of impact
- Monitor temperature gauge on your dashboard – dead locusts can reduce air flow to an engine and cause overheating
- Pull over & use cleaning agent and cloths/rags to remove residue from windscreen, wipers headlights and radiator air-inlet
2. If visibility is seriously impaired due to locust swarms:
- Slow down – gradually reduce your speed and stop only where it is safe to do so
- Turn off your engine – to avoid overheating
- Turn on your headlights – to alert oncoming traffic of your presence
- Remain in your car until swarm subsides
- When visibility improves apply water and insect cleaning agent and use cloths/rags to remove locust residue from windscreen, wipers headlights and radiator air-inlet
- Remain alert to danger of oncoming traffic
- Resume driving carefully
- By taking these precautionary safety steps, motorists can significantly improve their safety while driving through Australian Plague Locust swarms this Christmas and summer period.
What if locusts are found in back gardens?
The damage that large numbers of locusts can do to gardens may be reduced by the use of control agents. Nurseries and hardware retailers can supply home garden pack sizes of control agents and can advise of their safe use. It is very important that label directions relating to rates of applications and safety direction are carefully followed.
However, control agents will only provide some level of control - depending on when they are applied to a garden. Damage to gardens can occur quickly once a swarm of locusts arrives and landowners will need to act promptly.
While an application of control agents may continue to kill the locusts for a few days, the plants may still be significantly damaged before the locusts die. Plants such as trees, shrubs and lawns will usually regrow after the locusts have gone.
The most effective way to protect valuable trees or shrubs is to cover them with fine netting or shade cloth well enough to exclude the locusts. Do not use green coloured shade cloth/netting as this attracts locusts.
Information
Where can I get more information?
More information can be found on the Australian Plague Locust Commission website.
To report locust activity call the Locust Hotline on 1300 13 5559 and speak to a Customer Service Officer.
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