Fact Sheet: Dairy 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 dairy farmers 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.
Green pasture and fodder crops are highly susceptible to locust attack. Newly sown grass pastures are particularly vulnerable, as are the shorter pasture species. Young annual legumes may also be attacked. When locusts are present in massive numbers, all pasture and fodder crops are at risk.
Lucerne is typically green for longer than other crops, making it a prime feeding target. Damage is generally restricted to the stripping of leaves, but this may not always be the case. Established lucerne pastures (up to the 5th trifoliate leaf stage) may be less susceptible if paddocks have green grass weeds or there are alternative crops nearby.
When hay or silage is being cut and baled, many adult locusts will fly away. Locusts are likely to be roosting in plant or crop material during the cooler parts of the day, or at night if it provides suitable protection from predators, therefore baling should be avoided, where possible, during these times. There may be a reduction in the quality of fodder if locusts have eaten the leafy component of the plant. It is therefore important to remember that:
- established and recently sown pastures are susceptible to damage by locusts
- pastures that are drying off when locusts begin to fly are susceptible to damage
- locusts cause little, if any damage to mature pastures that have dried off.
What can I do?
You should treat locusts with insecticides when they are in the 'hopper' stage, before they can fly.
When locusts first hatch and emerge from the ground, they are often scattered. Treating locusts at this stage may be inefficient as some locusts may not have yet hatched.
Newly hatched locusts are very sensitive 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?
The use of chemical insecticides is the most effective method of treating locusts, particularly when they are still in the immature stages (called 'hoppers') and unable to fly. Hoppers may form and move as a 'band' or group, with up to thousands of hoppers for every square metre of the band. Spraying with insecticides at this stage is very effective and can greatly reduce numbers.
There are a number of products available for treating locusts. Farmers should seek expert advice from their chemical reseller or agronomist at to which chemical best suits their situation.
Dairy cattle can become contaminated by direct over-spraying of inappropriate chemical products, grazing of pastures or fodder crops that have been sprayed or onto which spray has drifted, and the feeding of fodder that has been directly or exposed to spray drift.
Dairy farmers need to consider the following when selecting which chemical to use:
Harvest withholding period (WHP)
This is the minimum time that must elapse between spraying the pasture/crop and harvesting the produce. The Withholding Period (WHP) is shown on the chemical label. Note that 24 hours must elapse to observe a 1 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. Unless a WHP is specifically listed for grazing or cutting, you must ensure that stock do not access treated areas, produce or crop waste.
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 period of time that cattle must be kept on clean pasture or feed, before entry to the milking herd, or slaughter for export, if they have been over-sprayed (aerially sprayed) with the insecticide or if they have eaten treated feed before the grazing/fodder withholding period has expired.
Export Grazing Interval (EGI)Livestock that have been over-sprayed or which eat treated feeds before the grazing/fodder withholding period for the insecticide has expired must not enter the milking herd, or be slaughtered for human consumption, until the EGI has expired, unless they have been kept on clean pasture or feed for the duration of the ESI for that insecticide.
Chemicals should only be used according to the label directions. All restraint and 'DO NOT' statements, WHPs and export intervals must be observed.
The biological insecticide containing Metarhizium anisopilae is the safest of the products to use, but can take up to 20 days to kill hoppers under cool conditions, which may be too long to prevent pasture or fodder crop damage.
Other chemical products work much quicker than the biological insecticide, causing locusts to stop feeding within a few hours, and to die within two or three days.
Products containing the active ingredient fipronil can provide a degree of residual control in situations where use of these products is appropriate.
When should I spray?
The best time to spray locusts is in the second and third instar stage, after the eggs hatch and before they are able to fly.
Warm, moist weather conditions are the most favourable for locust egg hatchings. Locusts are hard to spot when they first emerge as young immature hoppers. They are only about 3mm long and pale in colour. Newly hatched locusts can cause considerable damage and can consume half their body weight in food per day.
As hoppers are wingless and form large, slow moving bands, they provide a clear target for efficient chemical use. Spraying with insecticides at this stage is very effective and can greatly reduce numbers, with the period of about ten days to two weeks after hatching the most effective and cost efficient.
The most effective treatment is achieved when hopper band densities reach or exceed 80 hoppers per square metre. It may be more practical to treat bands at lower densities if they pose a danger to nearby valuable crops.
The locust life cycle diagram below shows where this stage occurs within the complete locust life cycle.
The hopper stage will last for around six weeks in total, depending on temperature, but the third instar stage only lasts for a week or so, making it important to carry out regular monitoring.
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?
Using a properly calibrated boom sprayer will minimise the risk of chemicals 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.
Managing your milking herd
Ensure you do not allow your milking herd access to any sprayed pasture or fodder crop until the grazing and fodder WHP for the chemical used has expired.
For example, if the grazing/fodder WHP is 14 days, then wait at least 14 days after spraying before:
- allowing the cows back into the paddock
- conserving feed off the paddock
- cutting and carrying feed from that paddock to feed the cows.
The insecticide sprayed on the pasture or crop will be broken down during the grazing/fodder WHP. Hay or silage made from the pasture or crop may retain a residue of the chemical for long periods, so do not bale or ensile the pasture or crop before the grazing/fodder WHP has expired.
If paddock feed is limited because these pastures and crops have been excluded from the normal rotation, then feed the cows on a feed pad, loafing pad, laneway or sacrifice paddock. Obtain advice from your local DPI dairy extension officer, factory milk supply officer or dairy cow nutritionist on what to feed.
If milking cows manage to enter a sprayed paddock or one that has been accidentally over-sprayed, notify your factory milk supply officer immediately and obtain advice. Then you should either:
- feed the cow clean pasture or a clean feed source for the duration of the ESI and withhold the milk during this period (do not feed it to your calves), or
- meet the EGI for the chemical before her milk enters the vat or is used for feeding calves.
If dry cows graze a sprayed paddock before the grazing/fodder WHP has expired, or if they are over-sprayed then they must not enter the milking herd until they have met either:
- the ESI or
- the EGI.
If selling stock, confirm all relevant EIs have been met before selling stock for slaughter. Remember to fill in the National Vendor Declaration (NVD) correctly. Penalties may apply for any false or misleading information.
Landholders need to follow the label directions and keep spray records. Contact the DEDJTR Locust Hotline on 1300 135 559 and ask for a spray record sheet.
Managing livestock and pastures
If there is a risk that a feed shortage could occur, it is important to plan now:
- Conserve feed by cutting hay or silage (prior to spraying) so that it can be fed to stock
- Use your current hay and stockfeed reserves for feeding livestock while sprayed pastures are still within the grazing/fodder WHP
- Buy enough hay or stockfeed for livestock until grazing/fodder WHPs have expired (request a commodity vendor declaration (CVD) from your supplier when purchasing any stock feed)
- You may need to organise a suitable feeding area (e.g. a laneway, sacrifice paddock, or stock containment area) if one doesn't already exist for your livestock. This area should not be adjacent to a watercourse or in an area where manure and effluent can reach a watercourse if it rains. Ensure stock have access to drinking water and shade during this period.
What about marketing produce?
Dairy farmers must ensure they control locusts while managing the risk of having unacceptable chemical residues in their milk or dairy products, hay or fodder stock feed. Unacceptable residues can lead to restrictions on, or closure of export markets to all Australian dairy farmers.
WARNING - Export of Treated Produce
Dairy farmers should note that relevant Maximum Residue Limits (MRLs) or import tolerances may not exist in export markets for milk, dairy products, hay or fodder stock feed treated with the products listed in this document, or they may be different to those established in Australia for domestic use.
If you are producing milk, dairy products, hay or fodder stock feed 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.
WARNING – Dry Crops and Fodder
All harvest, grazing and cutting for stock food WHPs, and EAFIs 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.
If a perennial pasture is treated, the period or interval may be observed in two phases. The first would be the amount of time between spraying a green pasture and dormancy beginning, and the second between dormancy breaking and the balance of the period or interval expiring. Note that grazing or cutting for stock food should not be allowed during this dormant period, and should wait until the period or interval has expired in the second phase. If a treated pasture or crop must be grazed or cut for stock food and fed to livestock within the EAFI, then the animals must be fed on clean feed for the entire period of the Export Slaughter Interval (ESI). For further information please visit www.safemeat.com.au
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 also be provided by your peak industry body, chemical reseller, agronomist or chemical manufacturer.
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.