Farmers on edge as orchards ‘hammered’ by rise of European earwigs

Farmers on edge as orchards ‘hammered’ by rise of European earwigs

While your cat might get a thrill out of hunting earwigs, farmers are less than impressed by the damage they do to crops.

Key points:

  • European earwigs eat a wide range of food including cherries, citrus and canola
  • A Riverland citrus grower says his orchards have signs of widespread damage from the insect
  • Entomology experts say the introduced species can limit the growth of new trees 

First detected in Australia in the 1930s, the introduced European insect species can be confused with the native predatory common brown earwig, which is usually larger, with an orange triangle on its back.

In South Australia, the citrus industry has been working with biological services experts to help growers detect, monitor and control European earwigs.

Entomologist Dr Paul Horne and entomology consultant James Altman said the insects were widespread throughout the country and mostly active at night during the cooler months.

“They are considered pests in many crops but have also been regarded by some as useful biological control agents of pests such as light brown apple moth, scales, aphids and mealybugs,” they said. 

“They produce an aggregation pheromone and can develop into high numbers, forming large groups in tight spaces away from direct sunlight.”

Check crops early

Citrus SA chair Mark Doecke said his citrus orchards in Ramco, in the state’s Riverland region, had been “hammered” by earwigs.

Mr Doecke says his citrus orchards have been heavily damaged by European earwigs.(ABC Riverland: Anita Ward)

“Some growers might be questioning whether they’re doing something wrong with fertiliser and water, but it’s actually earwigs,” he said.

“I’ve got blocks where 100 per cent of flowers and shoots have been eaten by earwigs.

“We’ve got some navels that they’re in, we’ve got some seedless valencias that they’re in, and they’ve been in some mandarins as well.”

Feeding by earwigs on slowly emerging bud growth can completely eliminate new foliage in the winter months.(Supplied: Biological Services )

European earwigs typically live for about a year, hatching in early spring before moving to tree canopies.

They can also be found hiding in areas such as bark crevices, fruit clusters, curled leaves and inside tree guards. 

Mr Doecke said citrus growers should check their orchards as early as possible.

“In the daytime you just see chewed leaves on the edges, especially the fresh growth or, in our case, there’s just no leaves they chew that hard,” he said.

Mr Altman and Dr Horne said control methods for European earwigs included using seed dressings, baits or insecticide sprays, and ensuring trunk guards weren’t buried into the soil at their bases. 

Soft immature leaves that have been damaged by earwigs show scalloped feeding symptoms on leaf edges.(Supplied: Biological Services)

“Whilst there is no threshold for earwig control, it is likely that damage similar to the previous season will occur if numbers are not lowered,” they said.

“Therefore, detecting the first signs of activity helps to time any possible control actions.”

However, Mr Doecke said the number of sprays available to control the “emerging problem” was limited.

“You’ve got to check pretty carefully with your packing shed, and your reseller, as to what you can use,” he said.

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