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Plague Locusts - Frequently Asked Questions 
The major difference between the grasshoppers and locusts is the capability of immature locusts (hoppers) to form dense aggregations called bands and of adult locusts to form swarms. Grasshoppers do not form bands or swarms. Bands and swarms generally form when the population density is high. 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 from 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. What area did the locusts cover? In spring 2005, very large numbers of hoppers emerged from eggs that had been laid near Mitiamo and Swifts Creek. Swarms of adults developed from these hoppers at both locations. Despite extensive control, eggs were laid in various locations within 100km of Mitiamo in December 2005 and around Swifts Creek in December 2005 and January 2006. The eggs hatched through January and February 2006 forming bands of hoppers. Very few hoppers survived to adults and no swarms were reported through late summer and autumn of 2006. What action did the State Government take in 2005-06? DPI and landholders ran an extensive control campaign in both the Mitiamo and Swifts Creek areas. Through spring 2005 and summer 2006, DPI sprayed in excess of 30,000ha of locusts, mostly hoppers, and ran incident control centres and control campaigns from Kerang and Swifts Creek. The expenditure in 2005-6 by DPI was $4.4m. The control campaign commenced in October 2005 and was not completed until March 2006 and was highly successful. Why do we have another locust threat in 2008? There was a significant migration of locusts to Northern Victorian from NSW (thought to have originated in QLD) in Autumn this year. Egg bearing locusts were observed over a large area and it's likely that significant amounts of egg laying has occurred. Although the current situation is similar to Autumn 2005, it differs in the following ways:
Even if interstate control programs are very effective, further incursions from NSW or QLD into Victoria are possible in and early Summer 2008. Has locust egg laying occurred? Yes. Locust egg laying occurred in Autumn 2008 and was recorded across an area of approximately 1.25 million hectares (ha) in northern Victoria. Locusts have now hatched and are starting to fly. These mature locusts may begin laying a second generation of eggs from late November and early December. Egg laying may occur in new areas where infestations have not been previously reported. In the right environmental conditions, locust eggs can hatch in as little as two weeks. Report sightings of egg beds or egg laying to the Locust Hotline: 1300 13 5559. Where exactly are the sites? The survey teams found female locusts that contained eggs (stage of maturity of the eggs inside the female locusts varied between sites) at the following locations – Barnawartha, Boorhaman, Carragamungee, Chillingollah, Chinkapook, (near) Corop, Dingee, Dookie, (near) Echuca, Elmore, Everton, Gunbower, Kanyapella, Kiewa, Lockington, Milawa, (near) Nannella, Norong, Oxley, Piangle, Picola, Pinegrove, Rochester, Rosewhite, Rutherglen, Serpentine, Terricks, Torrumbarry, Ultima, Whorouly. Why is the full extent of their egg-laying unclear? Egg beds were observed during the surveys at five sites located near Picola, Ultima and Yanac. As egg bearing female locusts were observed over a much wider area, it is anticipated that the actual distribution of egg beds will also occur over a wider area. Egg beds are however difficult to detect unless female locusts are observed during egg laying. The full extent of egg laying will not become apparent until the eggs begin hatching in 2008 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 dirt. 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. The eggs are buried below the surface. 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 the 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 therefore dig up clods of soil where locusts are seen drilling, or where holes are evident and 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 can lay up to five pods. Pods are laid at 5 to 7 day intervals. What causes locusts to hatch? Egg development occurs only in warm moist conditions. Given sufficient moisture and at 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 they hatch? Locust eggs laid in Autumn 2008 have now hatched and are maturing into adults that are starting to fly. These locusts can now also begin laying eggs from late November. What happens when they 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 to become adult locusts that are capable of flight. Australian plague locusts may disperse either by walking whilst hoppers or by flight as adults. At higher densities, the hoppers may form dense groups known as bands that move across an infested area en masse stripping the vegetation. Similarly, adult locusts can also form large groups called swarms which may invade and defoliate infested plants. Where will they spread? Flight is the main method by which locusts spread over large distances. This can occur 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 with the extent of spread 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? There has been some difficulty distinguishing the Australian plague locust from the wingless grasshopper and a number of 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 hindwings and distinctive scarlet line on the tibia (2nd segment from the body) 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. What do they eat? Most species of locust feed mainly on grasses. The Australian plague locust in particular prefers to feed on grasses and/or cereal crops such as wheat. However, when there is little green grass 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 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. 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 without inflicting damage. 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. Page Top New South Wales Where did they lay eggs in NSW last Autumn? In Autumn 2008, locusts were observed throughout a large part of NSW particularly the following shires: Riverina, Murray, Hume, Guldagai, Wagga Wagga, Narrandera, Condoblin, Forbes, Molong, Young, Central Tablelands, Dubbo, Coonabarabran and Tamworth. The extent of egg laying that has occurred throughout this area is unclear, but this will become more apparent as egg hatching continues over the next few weeks and as we obtain reports of more egg hatching. If they spread south, what will that mean for Victoria? It is difficult to gauge as the effect of any migration by adult locusts from NSW and possibly Qld into Victoria during late Spring or Summer 2008 is unpredictable. Small scale migration should only have limited effect unless this is concentrated into a small area in Victoria. The extent of any migration will also depend on when and where locusts arrive in Victoria. A migration during mid Summer into a very dry inland part of Victoria might therefore only have a limited effect if the migrating locusts find little food to sustain them when they arrive as they would be likely to die out shortly afterwards. In contrast, a migration arriving earlier in the season in a major cereal growing district could result in significant crop losses and would be difficult to control especially if it occurred close to harvest. Page Top Advice to Farmers Who is responsible for controlling locusts? In Victoria, the responsibility for control of locusts on private property rests with the landholder. What is the most effective way of controlling locusts? The most effective way of controlling locusts is to target the immature locusts (hoppers), especially when these occur in groups of hoppers 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, 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. It is also important to allow DPI staff access to privately owned land where required to facilitate monitoring. What can farmers do now? Locusts that hatched in early October are now maturing into adults and are starting to fly. These locusts can now start laying another generation of eggs. Landholders are being encouraged to remain vigilant and should contact the Locust Hotline on 1300 13 5559 to report: locust swarms; locust egg beds or locusts laying eggs on their property. If you see egg beds on your property, mark it with a peg or some paint so it is easier to locate and observe in future. It is important to control locusts during their early life-cycle stage - when they are hoppers and unable to fly. Once they become adults, control measures become much more difficult and expensive. Landholders will be able to control them at the early stage 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 alert beekeepers in the area. When should farmers or other landholders start getting ready? Now - locust egg hatchings started on 7th October in Stanhope and Dookie in North Victoria. This generation of locusts started to fly in mid-November and are now able to lay another generation of eggs. Page Top Government Action What is DPI’s policy on the use of control agents? DPI’s Locust Management Plan outlines DPI’s policies in relation to Plague Locusts and 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. DPI’s policy on control is:
Will Government provide control agents? The state government will purchase control agents for use solely by DPI staff or aerial or ground applicators operating under contract and supervision by DPI staff operating in accordance with the DPI’s Locust Management Plan and 2008-09 Locust Response Plan. Will Government spray locusts? DPI will undertake targeted control of locust hoppers in specific circumstances on public or private land to reduce the locust population and minimise dispersal of adult locusts. How will the spraying be conducted? The control agents will be 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, only ground application will be feasible. The choice of the application will follow guidelines and policy described under the DPI’s Locust Management Plan (version 6.0). Which control agents will DPI use? The current version of the response plan lists control agents that contain the following active ingredients:
Are the control agents dangerous? All control agents are dangerous by their very nature. While the control agents being used for locust control are not the most toxic of all control agents to humans they must be treated and handled with care. 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 minimising the risk that insecticide will drift into areas that should not be treated. DPI will only use registered control agents in accordance with the labels and will observe all directions. How will DPI minimise the risks when it sprays In all its handling of control agents, DPI will strictly comply with all safety requirements. In selecting areas to be sprayed, 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 that should not be sprayed, animals, schools water bodies, houses, etc. 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 with-holding periods; crop safety recommendations; rates and methods of application; and only allowing trained & certified people to apply the control agents. Page Top Possible spread What will happen if locusts spread to Melbourne and major regional centres? If locusts do manage to reach Melbourne, they will occur as individual adults locusts during the day or more likely as swarms migrating long distances overnight. What action should motorists take? Australian Plague Locust swarms are predicted over the holiday season and 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. DPI and RACV have developed some tips for motorists so they know what they should do:
Before you leave home:
Driving through a swarm of Australian plague locusts: 1. If visibility is somewhat impaired due to locust swarms
2. If visibility is seriously impaired due to locust swarms:
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 will 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? Daily situation updates are available on the front page of this website. More information can also be found on the Australian Plague Locust Commission website http://www.daff.gov.au/animal-plant-health/locusts. To report locust activity call the Locust Hotline on 1300 13 5559 and speak to a Customer Service Officer. |
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© The State of Victoria, 1996 - 2008.
This document was published on 21/11/2008.