Fact Sheet: Organic Industry
Australian plague locusts naturally inhabit the far north west of New South Wales and adjacent areas of Queensland and South Australia, an area known as the channel country.
They generally inhabit rural regions in relatively low numbers, but under favourable weather conditions, they can multiply and migrate in large swarms to southern agricultural areas in southern Queensland, New South Wales, Victoria and South Australia and cause severe damage to pastures, field crops, and vegetables.
Although locusts are not native to Victoria, they may be seen in varying densities from season to season particularly in northern Victoria.In any given year, it is possible for locust swarms to migrate into Victoria from interstate. The Australian Plague Locust Commission provides forecasts on the likelihood of this occurring.
The following information will help land managers plan their risk management strategies for treating locusts if they are present in regional Victoria.
Risk to crops
The Australian plague locust 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. A series of similar information notes have been developed for growers in these industries and should be referred to for more specific information.
When is the best time to act?
The best time to treat locusts is when they are in the 'hopper' stage, before they can fly. Programs to treat adult flying locusts are generally ineffective.
When locusts first hatch and emerge from the ground they are often scattered. Treating locusts at this stage may be inefficient, as some may not have yet hatched.
Newly hatched locusts are vulnerable and without food and shelter they are susceptible to premature death. As these locusts develop, they form high density bands and this is the best time for treatment activities.
What are my treatment options?
Using an approved biological insecticide containing Metarhizium anisopilae fungus to treat locusts is the safest and most effective way for organic growers to mitigate the impact of locust damage.
Growers should seek expert advice from their chemical reseller or agronomist as to which chemical best suits their situation.
NOTE: There are several formulations of this biological insecticide so it is vital that growers contact their certifier before making any decision to purchase and use any locust treatment product. While the use of a particular product may be acceptable under Australian certification standards, the standards applicable in other countries may be different.
The fungal spores in the Metarhizium insecticide cause an infection inside the locust's body which leads to death. A kill rate of 90% to 95% can be expected.
As this mode of action is slower when compared to alternative chemicals such as organophosphates and synthetic pyrethroids (which stop feeding within a few hours, and kill locusts within two or three days), crops and pastures treated with this biological insecticde will remain at risk for longer. It can take up to 20 days to kill hoppers under cool conditions (10-14 days under warmer ideal conditions). Note that while it may take 10 - 20 days for the locusts to die, feeding may cease much earlier, so while treated hoppers may remain on crops, they may cause little damage.
Who can provide further assistance?
It is strongly recommended that organic growers consult their organic certification agency about the use of any products to treat locusts.
It is also recommended that organic growers talk to neighbours who may use conventional chemical options to treat locusts that could potentially impact on the organic status of a farm. Identifying sensitive areas and the establishing of buffer zones are options to minimise these risks. These issues should be discussed well in advance of spraying beginning.When choosing a chemical treatment option, landholders need to consider the following if applicable:
Harvest withholding period (WHP)
This is the minimum time that must elapse between spraying the pasture/crop and harvesting the produce. The WHP is shown on the chemical label. Note that 24 hours must elapse to observe a one day WHP. Unless a WHP is specifically listed for grazing or cutting, you must ensure that stock do not access treated areas, produce or crop waste.
Grazing or cutting for stock food (WHP)
This is the minimum time that must elapse between spraying the pasture/crop and grazing that feed or when the pasture/crop can be cut for hay or silage.
Export animal feed interval (EAFI)
This is the minimum time that must elapse between the application of a chemical and grazing or harvesting the crop/pasture for animal feed.
Export slaughter interval (ESI)
This is the minimum time that must elapse between removal of grazing livestock to clean pasture or feed and slaughter, where the livestock have been grazing the crop/pasture prior to expiry of the export animal feed interval
Export grazing interval (EGI)
This is the minimum time that must elapse between the application of a chemical and slaughter of the stock, where grazing has continued on the crop/pasture from the time the chemical was applied.
Are there receival standards for locust parts in grain?
Bulk grain handlers have receival standards for locust body parts in samples, and for grain that has been damaged by locust feeding. Locust body parts may also change the smell and colour of grain.
Locust body parts detected when grain is delivered to grain receival centres may result in the grain being downgraded to feed quality, or rejected.
It is possible to clean grain to remove locust body parts, but this is time consuming and expensive, and may not be logistically possible during the harvest period. Receival standards can be obtained from www.graintrade.org.au or grain traders.
When should I spray?
The most effective time to spray locusts using Metarhizium anisopilae is in the early nymphal stages of growth because of how long it can take for the insect to be killed. Using a biological insecticide, such as Metarhizium anisopilae, differs slightly from other insecticides due to the extended time it takes for locusts to die and the benefit of a longer residual period.
Given this, it may be beneficial to treat a whole area when locusts are widely dispersed, however it is certainly more efficient to spray once hoppers form large, slow moving bands, providing a clear target for efficient insecticide use. Spray 10-15m in front of the band and then treat the band itself.
The hopper stage will last for approximately six weeks in total, depending on temperature, but the third instar stage only lasts for a week or so, hence it is vital that you regularly monitor hoppers.
The best time of the day to spray hoppers is late morning through to late afternoon when they are most active and most visible.
DEDJTR doesn't recommend spraying flying, adult locusts as it is very difficult to do safely and effectively. Individual landholders may make a business decision to spray flying locusts for the protection of valuable crops - but must obey withholding periods and follow the directions on the label of the chemical product used.
Whilst there is no conclusive data, ploughing egg beds may have some effect on loose, sandy soils. However, it unlikely that ploughing heavier soils will have any great effect on egg beds as pods will be more protected in soil clods.
Landholders should concentrate their efforts on treating locust hoppers after they have hatched and when they form dense bands on the ground.
What equipment should I use?
Conventional equipment can be used to apply Metarhizium anisopilae. Using a properly calibrated boom sprayer will minimise the risk of chemical sprays drifting outside targeted areas.
While misters may appear to apply chemicals efficiently, they present a greater risk of spray drift, increasing the risk of unacceptable residues in nearby crops, livestock, or other areas.
What about marketing produce?
If organic growers only use the approved biological insecticide to treat locusts, there will be no issues relating to the marketing of organic produce apart from the potential for contamination of the produce with locust bodies or body parts.
If other chemical treatment options are used by organic farmers, the risk of chemical residues in their produce must be appropriately managed. If other chemical options are used, the organic certification agency should be notified, and it is likely that the organic status of the land will be affected.
Unacceptable residues in produce can lead to restrictions on, or closure of, export markets to all Australian growers for the particular produce.
WARNING - Export of Treated Produce:
Growers should note that relevant Maximum Residue Limits (MRLs) or import tolerances may not exist in export markets for produce treated with the products listed in this document, or they may be different to those established in Australia for domestic use.
If you are growing produce or rearing livestock for export, check with your peak industry body or the manufacturer of the product for the latest information on MRLs and import tolerances before using the product. Your chemical reseller or agronomist may also be able to provide advice.
WARNING – Dry Crops and Fodder:
All harvest, grazing and cutting for stock food Withholding Periods (WHP), and Export Animal Feed Intervals (EAFI), are based on a chemical product being applied to a crop/pasture that is still growing at the time of application and for the duration of the period or interval. The reason behind this requirement is that the breakdown of chemical residue levels in plants slows, and may stop, once the plant is no longer growing or alive.
DO NOT apply a chemical product to a crop/pasture, where a WHP or EAFI applies, unless the crop/pasture is still growing (green) at the time of application and for the entire duration of the relevant period or interval, or if expert advice is sought and this risk is managed, including pre-harvest residue testing.
Specific market advice can be provided by your peak industry body, chemical reseller, agronomist or chemical manufacturer.
Look out for bees
Some crops need insects to pollinate flowers and bee hives may be placed near or on your property to assist the pollination process. If you or your neighbours are in this situation, apiarists should be contacted and informed of your intention to spray, enabling them to manage the risk to their hives. Other options include waiting for suitable weather conditions, when hives are upwind of the treatment area or during times of low bee activity in the early evening.
Some chemicals contain 'DO NOT' label statements that specifically prohibit the use of the chemical when bees are foraging in the crop to be treated. Complying with these statements is a legal requirement.
What are my obligations?
Landholders need to be vigilant in monitoring their crops, pastures and known locust egg beds for evidence of activity and crop damage.
While we cannot eliminate the locust threat completely, a collaborative approach with public and private landholders working together can reduce the effect on vital food production areas, the natural environment and rural communities.
All Victorians should report locust activity and known locations of egg beds to the DEDJTR Locust Hotline on 1300 135 559.
Private landholders are responsible for treating locust hoppers on their own property.
All chemical use must be in accordance with State laws and regulations, including record keeping requirements.
Information on the current locust situation can be found at www.agriculture.gov.au/pests-diseases-weeds/locusts/current.
Information on locust biology and management can be found at www.agriculture.vic.gov.au/agriculture-and-food/pests-diseases-and-weeds/pest-insects-and-mites/plague-locusts
Report locust sightings to the DEDJTR Locust Hotline on 1300 13 5559.