On the hop

Voracious spur-throated locusts are on the verge of stripping the northern Wheatbelt of emerging crops.

The locusts, which are hungrier and harder to control than the Australian plague locust, have already wreaked havoc on Carnarvon’s horticultural crops — and now they are moving south.

Department of Agriculture and Food (DAFWA) entomologist Svetlana Micic said the locusts, which ate anything from cereal crops to fruit trees, were a subtropical pest but tended to move into areas where summer rain occurred.

A recent survey found the locusts between Geraldton and Carnarvon in areas that had summer rain.

Spur-throated locusts were in low numbers around Carnarvon last year and the area’s last recorded outbreak was in 1945.

Although found intermittently, there has never been a recorded outbreak of the locust in the Wheatbelt.

However, croppers north of Geraldton have reported significant numbers of nymphs. They fear if the pest isn’t controlled, April’s emerging crops will be decimated.

Ms Micic said nymphal densities of 20 per square metre or more posed an economic threat to crops and just one to three adults per square metre would cause damage.

The most effective means of control is aerial spraying, but it is expensive. DAFWA has advised growers to consider how much they would be prepared to spend on control.

“They are a larger locust species and the rates required for control are a lot higher (than for the Australian plague locust),” Ms Micic said.

“It’s difficult to ground spray, because they are very mobile. A better option would be a residual spray.”

Unlike Australian plague locusts, the nymphs do not form high density bands and can roost in trees before returning to other areas to feed.

“There can be swarms in autumn and winter and we expect some swarm movement in more southern areas,” Ms Micic said.

Within a few weeks, most of the locust population will be fledging adults, and Binnu grower Tom Powell is concerned.

Mr Powell, whose family have farmed in the area for almost 50 years, was hoping to capitalise on good subsoil moisture gained from 250mm of summer rain.

“We’ll probably be seeding just after Easter and the locusts are going to be there waiting to eat everything,” he said.

“They’ve hatched in the past three weeks and there are a lot of nymphs. Everyone north of Mullewa Road is affected to some degree.”

For Carnarvon growers, it is yet another hurdle in what was a difficult summer.

Carnarvon grower Stan Kostanich said combating spur-throated locusts was expensive.

“I have been spraying every day to keep them out, and it’s costing me an arm and a leg,” he said. “I will spray them and another lot will come in from the bush the next day.”

Already having lost a small patch of tomatoes, Mr Kostanich said he was keeping a close eye on his young grape vines.

“It’s nearly costing me what the flood did. The pennies are adding up,” he said.

Carnarvon Growers Association agronomist and organic grower Mel Brady said most fruit and vegetable growers in the area had been affected.

“It’s going to have a big impact on the next mango crop, because the new shoots are being eaten,” she said.

“The locusts are also chewing the banana leaves, which is allowing light to get in and burn the bananas.

“Even the feed on stations has been affected.”

A DAFWA spokeswoman said the department was monitoring spur-throated locust activity and providing advice on control options.