THE TIME TO worry is when favourable weather produces large hatchings of baby locusts on outback plains.
A band can be several kilometres wide and a hundred metres deep, with young locusts crowded at densities of 5000 or more per square metre of ground, all marching with determination in one direction.
They can crawl a hundred metres a day, mowing down all vegetation, eating each other if they run out of herbage, until such time as they moult into winged adults, when they migrate at night, sometimes travelling hundreds of kilometres, suddenly descending on crops and pastures, of which they can consume a thousand kilograms in a day. Sugarcane, wheat, maize, barley and oats are some of the crops they hit. I have driven through a locust plague in inland Queensland, and it was like driving through fluttering rain, except for the colourful mess they left on the windscreen.
Australian plague locusts. (Image Credit: Taronga Zoo)
Australia has three destructive species, but the Australian plague locust (Chortoicetes terminifera) does the most harm. The others are the spur-throated locust (Austracris guttulosa) and the migratory locust (Locusta migratoria), a species we share with Africa, Asia and Europe, which happens to be the world’s most widespread grasshopper. A genetic study found it hasn’t been in Australia more than a couple of hundred thousand years. Locusts have been known to cross the Atlantic Ocean, which is further than they flew to reach Australia from Asia.
Land clearing has benefited locusts by providing them with more pastures to feed on, and they like lush imported pasture grasses. Australia has the Australian Plague Locust Commission to monitor and help manage outbreaks. Emerging infestations are sprayed. This kills other insects in the vicinity.
Locust plagues are an opportunity for feasting by birds. Magpies, ravens, kestrels and kites are some that benefit, along with ducks, herons and sparrows. One straw-necked ibis swallowed 699 locusts in one greedy session.
The Book of Leviticus explains that locusts are an acceptable human food, and an Israeli company, Hargol Foodtech, has taken that to heart by establishing a large farm of migratory locusts, where their bodies are converted into edible powder. The farm boasts extremely low greenhouse gas emissions, low water use and zero waste.