Hoppers Traditional Cache

To find this cache you need to think locust! What is a locust you ask? Closely related to the grasshopper the locust belongs to the Order Orthoptera and is a plant eating insect with powerful back legs for jumping. There are over 700 species of locust and grasshoppers in Australia but there are 3 that are considered a serious pest - the Australian Plague Locust, Spur-throated Locust and the Migratory Locust.

Locusts and grasshoppers, for the most part, look the same but they behave very differently. Grasshoppers tend to get about by themselves and do their grasshopper thing whereas locusts can be solitary (which is good) or gregarious where they form dense swarms (which is bad, for us anyway) . Locust swarms are infamous across history. Plagues were mentioned in the Bible, the Quran, in ancient Chinese texts and images of locusts have been found inside ancient Egyptian tombs. Links between locust plagues and human disease outbreaks have also been reported in China in 311 AD however it is likely that the increase in locusts provided food for large populations of rats (and their fleas) which caused the downfall of human populations.

Their behaviour depends on the size of the population. Low populations of locusts behave as individuals. High populations of locusts start grouping together and form the characteristic swarms we are familiar with in a locust plague. This behaviour can even have a physical effect on the locusts and can alter their body shape, colour, fertility, survival and migratory behaviour. The differences can be so great between an individual locust and a swarm of locusts that for some time they were thought to be two different species.

Locusts lay their eggs by pushing their abdomen down into the soil and laying a pod of eggs then sealing the hole with froth to protect the eggs from predators and disease. They hatch and scramble to the surface and begin to forage. A locust goes through 5 life stages (known as instars) to reach adulthood and they moult between each stage to grow in size. After about 5 weeks they undergo a final moult to become an adult where they finally develop their wings and can fly.

Locust laying eggs in the soil

Locusts are considered one of the most serious pests in Australia due to the frequency of outbreaks and the sheer scale of damage a swarm can inflict. They cause widespread damage to crops by eating the vegetation. They have even been reported to feed on other green things such as shade cloth. They eat crops and food for livestock and farmers are faced with huge costs both for control and loss of income due to crop losses.

The right combination of conditions has to be present for a plague to form. High rainfall over spring and summer throughout the locust home range boosts the breeding ability of the population and leads to swarms forming in autumn. Summer breeding can also occur with several batches of eggs laid during autumn. This causes large populations of nymphs during the following spring which leads to swarms over summer. Swarms in spring can cause severe damage as winter crops are nearing maturity and summer crops are just emerging.

During a plague groups of “hoppers” (young locusts with no wings) form dense groups called bands. They slowly march across the landscape consuming crops as they go. The image below shows damage caused by a swarm. A swarm covering just 1km⊃2; can eat 1 tonne of vegetation per day. Once they have reached their adult phase and grow wings they can take flight and cover vast distances. It’s not uncommon for a swarm to migrate several hundred kilometres in a single night with favourable weather conditions. Swarms typically extend for several kilometres and migrate during the day potentially moving up to 100km in a week with favourable winds.

Damage caused by locust swarm

Landowners are responsible for managing locusts within their own property. Agencies such as Local Land Services and the Department of Primary Industries are on hand to provide technical advice and conduct surveillance for the presence of locusts. They can also help landowners manage outbreaks once the population has gone beyond the ability of the farmer to manage on their own. The Australian Plague Locust Commission monitors populations and helps to predict and manage outbreaks.

High density swarm over a wheat crop

Control of locusts isn’t easy. They are a highly mobile insect and (in the adult phase) can quickly jump from one area to another in short spaces of time. Farmers can spray the hoppers on the ground but they only have a window of about 3 weeks (between hatching and adult phases) to be able to do this. Areas where eggs have been laid can also be cultivated to break the cycle but this if often difficult as locusts tend to lay their eggs in hard soil, not in paddocks but on roads or claypans. Once all ground control options have been exhausted the Australian Plague Locust Commission and/or DPI may organise aerial spraying and work with landholders to achieve this difficult and dangerous work. Unfortunately natural predators are of little use in controlling the population during a swarm due to the sheer volume of insects. Swarms contain millions of insects and quickly outnumber the usual predators.

A useful tool in the management of locusts is surveillance. Knowing where locust activity is taking place can help make predictions on the likelihood of a plague and allow farmers and agencies time to prepare. Locust activity can be reported to the Australian Plague Locust Commission on 1800 635 962 or to Local Land Services.