Locusts — who are they and why are they here?

You’d think the heavy winter rains in Australia’s south-east that broke the drought and filled a struggling river system would have been welcomed by all. But the Big Wet, which looks likely to yield some bumper crops for farmers, may also come at a price. The downpour has been the equivalent of mood lighting and a Barry White record for one of our most feared pests — Chortoicetes terminifera, the Australian plague locust.

The widespread rainfall and warmer temperatures have seen large numbers of locusts begin to hatch across wide areas of regional Australia, leaving more than just farmers nervous about the mischief they might cause. Crikey spoke with Chris Adriaansen, director of the Australian Plague Locust Commission, about how a few billion scary grasshoppers might ruin it for everyone.

Why are there going to be more locusts this year than in the past?

It’s a seasonal thing that is a combination of rainfall, aggregation and how each generation multiplies. Australian plague locusts have four generations each season and each generation can multiply on the previous if conditions are good. It’s an unfortunate coincidence of nature that the same conditions that gave rise to a good crop and grassing situation have led to this locust plague. Primarily it’s all about widespread rainfall and good temperatures.

When are the locusts expected to hatch?

There have already been some hatchings and we have seen some significant locust populations in the north-west of NSW. Those locusts hatched 7-10 days ago and have aggregated in large numbers (full predicted locust hatching dates can be found here).

How many locusts are we talking?

How many grains of sand are there on a beach? We are talking literally billions of locusts. Anything up to 5 million hectares of land will be infected by locust eggs, so do the maths if you have a calculator with enough zeroes.

How many locusts are there in a swarm?

According to the APLC, a swarm of Australian plague locusts, covering one square kilometre, could contain anything from 4 million to over 50 million locusts. The size of a typical Australian plague locust swarm is highly variable, from one to over 25 kilometres squared

Which areas are at greatest risk from a locust plague?

We’ve got a number of key risk zones. The central-west region of NSW, the Riverina region of NSW, the north, in particular north-west, of Victoria, and the eastern Flinders region of South Australia.

How long will it take before the locusts begin to cause problems?

Locusts have five stages of development as nymphs when they have no wings, so we won’t see any swarms of locusts for at least another six weeks. The majority of the high density areas in places like Victoria are yet to hatch, so it will be at least eight weeks until we begin to see swarms in those areas. But the swarms are only part of the risk. The nymph’s sole purpose is eating and growing, so they can still do quite an amount of damage.

How far and how quickly can they move?

When they’re at the nymph stage they don’t move very far at all, because they don’t have wings they can move around 200-250m per day. Once they grow wings it’s a different story, they can move around 20-40km per day. Overnight they can fly up to 700km, as long as they get the right wind conditions. So basically they can be here today and gone tomorrow. But I don’t think we will be seeing that this time, there is just too many of them.

Which industries are at greatest risk from a locust plague?

The normal diet of these species is grass and the associated plants. Probably the most significant risk is to grain crops, so wheat and barley and other crops such as canola and the pastures areas where livestock grows.

What kind of damage can they do to crops?

They can completely wipe out a crop. If they don’t take 100% of the vegetation, they can destroy large amounts of plant material so that a crop’s yield is significantly reduced.

Is there a chance they could move from farms into some of the larger regional towns, and even cities?

We do see that from time to time. Certainly the swarm of locusts in April did move into some larger regional centres. In the Mildura area during April we saw a number of community events halted, including sporting events. The local airport was also closed and Virgin Blue halted their flights into Mildura because of the problems posed by the locusts.

What kind of damage can they do to cars?

One is obviously visibility; these locusts are going to be well fed and fat, so when they hit the windscreen the fat will be smeared everywhere. The other issue is the blocking of air intakes, which can lead to an engine overheating.

Who is in charge of the response to the locusts?

It’s a collaborative arrangement. APLC has a role and responsibility; our stated mandate is to monitor and manage locust populations that are found in more than one state. But each of the state’s agencies has a key role to play. What we have done since April is bring everyone together and plan a response so we can have this covered as best we can.

How are you managing the locusts?

There are range of different control agents that can be used to manage the locusts, whether from the ground or air. Landholders and ground control contractors undertake ground-based spraying, while the state controlled agencies and APLC undertake aerial spraying.

Are the pesticides used on locusts a problem for humans?

First of all of these pesticides are registered with the Australian Pesticides and Veterinary Medicines Authority. Secondly, we leave a very significant buffer zone around human activity, water courses and restricted or significant areas. Thirdly, we have developed a number of techniques in that we don’t blanket spray areas, we leave 90% of land area untreated and then leave it up to locusts to discover the discreet chemical strips we lay down.

This is not a pest eradication program; locusts are a native insect and we are trying to manage the issue as best we can.