I’ve found some adult locusts in my back garden/in the paddock. What should I do, will they eat a lot?

Adult locusts will potentially eat any vegetation that is green or partially green, however possible damage depends on locust numbers. A few scattered adults in a garden, crop or pasture are unlikely to cause any noticeable damage and there may be no need for action.

In gardens, the best strategy may be to protect valuable plants and shrubs with insect mesh or shade cloth to prevent access from locusts. Ensure mesh is not green as this colour is attractive to locusts. Alternatively, a household or garden insecticide can provide quick knockdown of locusts but it will not prevent re-invasion by other adults.

Higher numbers of adults could cause extensive damage in a relatively short time. Landowners encountering adults in crops or pastures need to assess locust numbers and decide whether potential losses are worth the cost of undertaking chemical treatment. A treatment will not prevent re-invasion of adults into crops or pastures.

An interstate swarm of locusts earlier this year. Photo courtesy NSW Dept of Industry & Investment.

What's the best way to spray them if I've got the time or capability? Is there a time of day when they're likely to be settled? Will particular insecticides be more effective with adults than others?

Adult locusts are highly mobile insects and control is very difficult when they are on the wing. The best time to spray adult locusts is when they are settled on the ground, usually at dusk or early in the morning. Obstacles such as tree or scrub lines can affect locust behaviour and cause them to settle or funnel along these lines. They also settle in cold or windy conditions which could provide more opportunities for chemical control. However, wind conditions that are gusty and variable may not be suitable for spraying. Insecticides can provide rapid knockdown of adult locusts but re-invasion by other adults could still occur. Check for locust movement in and out of adjacent pasture paddocks.

Treatment should directly target locusts. Most insecticides kill locusts both through direct contact or ingestion of insecticide from treated plant material. Residual control will not usually exceed a day or two at most. Insecticides are not effective repellents and therefore it’s not possible to spray before a swarm arrives to prevent them entering a crop.

When undertaking treatment, use only insecticides registered (or permitted) by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for locust control in the relevant crop, and carefully read and fully understand insecticide product labels before treatment. For a full list of approved chemicals see specific fact sheets listed in http://www.pir.sa.gov.au/locust/factsheets  For further advice also check with your chemical reseller. Always use the full recommended application rate and correctly calibrate spray equipment (whether boom, mister or aircraft) to achieve adequate spray coverage. All registered insecticides should provide comparable control of locusts if label directions are followed and there is adequate coverage.

How long do locusts live for after they take to the wing?

Adult locust activity and development is driven by environmental conditions (i.e. rainfall, green feed and temperature). They typically persist for several months and will usually die off fairly soon after finishing their egg laying. In warmer conditions, with plenty of feed, they can complete development and egg laying more quickly. In milder conditions locusts will develop slower and may persist for longer. Alternatively, if conditions are very dry, adults may die off before having the opportunity to lay eggs.

Will they lay eggs in my back garden, or back paddock?  What should I look out for?

Adults can become sexually mature within two weeks of developing wings if there is enough green feed available. The female selects suitable sites for egg laying by drilling test holes in the ground with her abdomen. Locusts usually prefer to lay their eggs in hard, bare ground in open areas such as roadsides, tracks, fence lines, dry land flats and sparsely vegetated pasture paddocks.

Image of locusts mating in red soil

Eggs are laid in pods at a depth of around 2 cm to 5 cm in autumn and 6 cm to 8 cm in summer, depending on soil type. Each pod contains 30 to 50 pale yellow banana-shaped eggs 5 mm to 6 mm in length. One female can lay up to four pods before dying. If conditions are dry, adult locusts may move on or may die off without laying.

Locust eggs as laid in ground. Photo courtesy NSW Dept of Industry & Investment

If they do lay eggs, how long will it be before there are hatchlings?

Eggs need warm conditions and soil moisture for development. During summer, eggs may hatch in 14 to 20 days (temperature dependant) while eggs laid in autumn usually remain dormant during winter and hatch in spring as soil temperature increases. In southern Australia, hatching can occur from spring through until autumn.

An autumn generation of locusts could potentially occur in home gardens if invading locusts are carrying eggs. Towards autumn, any eggs laid are likely to hibernate until spring when they will hatch. Locusts hatching in gardens, whether autumn or spring, should be relatively easy to control with an insecticide.

How long will it be before locusts take to the air?

After hatching, nymphs (hoppers) develop through five growth stages. Wing buds become progressively more noticeable through each stage until at the final moult (fledging) a young adult emerges with fully developed wings. Hoppers complete development to adult stage in four to eight weeks, but more rapidly at warmer temperatures. During the first week the bodies and wings of newly fledged adults harden up before they are capable of sustained flight.

When the majority of hoppers have fledged, the adults concentrate into groups called swarms which make low drifting flights up to 50 metres high, covering up to 10 to 20 kilometres a day. Flight behaviour depends on the adult development, wind speed and temperature. Long distance migration can occur at night if there has been enough green feed available to enable fat accumulation.

Where do adult locusts naturally gravitate to once they're on the wing? Will they head for water (and eventually out to sea) or is that a myth.

Adult locusts are a highly migratory insect capable of moving large distances on suitable weather systems. The direction of migration depends on adult development, thermal activity and wind direction at the time of migration. In suitable conditions they can travel many hundreds of kilometres in a single night. Sometimes weather systems result in migration to areas unsuitable for successful breeding. Locusts have been reported washed up on shores.

I've got some grapes growing in my back yard/or paddock, will they decimate the leaves on my vines?

Adult locusts can feed on most green plant material including grape vines. The amount of potential damage depends on locust density. High density adults could cause significant stripping of leaves and damage young vines and new buds, however at lower densities adults may cause relatively minor damage.

Mature locust on weed

I've got veggies growing in my garden, what should I do if I get a whole load of adults fly in?

If your garden is invaded by adult locusts, homeowners should first consider cost-effective non-chemical methods to minimise damage. Valuable shrubs and plantings can be protected by covering them with insect mesh or shade cloth. Ensure the mesh is not green as this colour is attractive to locusts. Screens should completely enclose susceptible plants to prevent any access by locusts. All entrances and openings to greenhouses should also be covered to prevent locusts entering.

Small numbers of locusts may be controlled by catching them with a net and squashing them. Insecticide sprays are an option for achieving quick control but will not prevent reinvasion by other adults. No insecticides are effective locust repellents, therefore it is not effective to spray before infestation to try and protect plants.

The best time to spray is early in the morning or at dusk when adult locusts are settled on the ground. When choosing a household or garden insecticide, seek advice from your local garden centre or chemical reseller and use any product only as directed on the label.

Will the adult locusts do damage to my fruit trees - I've got some trees out the back, will they eat the foliage on these?

Locusts prefer to feed on grasses but will feed on most green plants including vegetables and fruit trees. Small numbers of adults are not likely to cause significant damage but some stripping of leaves could occur at higher densities.  If you’re concerned about the risk of locust fly-ins, consider temporarily covering fruit trees with a shade cloth or fine mesh to prevent damage. Ensure the mesh is not green as this colour is attractive to locusts.

Is there any plant or garden husbandry we can carry out to make our gardens less attractive to adult fly-ins? If I put sprinklers on will that shoosh them away?

Locusts are attracted to green plant material. Removing excess weeds and covering valuable green plants with a shade cloth or fine mesh that is not green in colour will help protect plants and may reduce the amount of green vegetation that is visible to locusts. Sprinklers are unlikely to repel locusts.

Will heavy rainfall we’ve had in recent weeks reduce locust populations?

Heavy rainfall slows locust activity but will not significantly reduce adult numbers. Adult locusts are highly mobile and are unlikely to be caught in flooded areas. Locusts will again become more active when conditions warm up.

March 2011