Citrus industry trial targets costly pest

Citrus May 17, 2023

Wasp traps developed and trialled in South Australia could be the key to controlling a pest that costs the national citrus industry “tens of millions” of dollars a year.

Fruition Garden Citrus gall wasp Traps – made by agricultural technology company AgNova in conjunction with the University of Adelaide and Citrus South Australia – were used by some South Australian growers in spring to better identify the emergence of the pest in citrus orchards.

Knowing when the Australian native pest hatches, ensures growers can apply a crop protectant at the most effective time to protect their trees and fruit.

AgNova Surround on citrus leaves makes the plant unattractive to CGW and protects the crop from sunburn. 

A crop protectant such as Surround hinders the Citrus gall wasp (CWG) reproduction, breaking its lifecycle.

Preventing the next generation of CGW will improve the profitability of the Australian citrus, according to grower and Citrus SA chair Mark Doecke.

“It’s an emerging problem,” he said.

“In South Australia, we have gall wasp mostly in lemons, rootstock in other citrus and a couple of orange varieties.

“I know of an orchard that’s pure gall wasp, there’s nothing left, all the citrus fruit is just 50mm because the tree can’t get enough sap to it.

“There’s no market for small fruit and if you send it to juice, you may as well throw it in the paddock. It’s worth nothing.”

CGW is unique to Australia. Adult CGW are abundant for four weeks from late October to mid-November.

This destructive pest lays eggs in the fresh growth of citrus trees. Infestations weaken trees, cause branches to die and limit fruit production.

Mr Doecke estimated CGW costs Australian citrus “tens of millions” of dollars annually.

Citrus SA was instrumental in developing the Fruition Garden Citrus gall wasp Traps.

The AgNova Fruition trap developed in conjunction with the University of Adelaide and Citrus South Australia. 

“The industry has a huge problem with Citrus gall wasp and because we are the grower body in South Australia, we have a responsibility to help growers,” Mr Doecke said.

“We initiated the work with the University of Adelaide, researchers discovered the volatile – what the wasp is attracted to – and we went from there, developing the traps with AgNova.”

Many growers involved in the trap trial combined the traps with the crop protectant, Surround for best practice insect and sunburn protection.

US crop nutrition and technology company Tessenderlo Kerley International business director Peter Barrows was involved in the development of Surround.

It’s been used globally for 20 years, mostly for fruit sunburn protection.

Mr Barrows said its unique properties means it repels insects in a different way than a conventional pesticide.

“There’s no chemical activity, it does not kill the insect,” Mr Barrows said.

“Instead Surround creates an environment in which when insects land on a treated plant they have touch cues that indicate they aren’t in the right place to lay eggs or feed. Reducing egg laying reduces new galls and the next generation of CGW.”

When it comes to citrus crops, Mr Barrows said the Fruition Traps ensure optimal timing for initiation of a control program based on Surround. It also has the added benefit of Surround providing proven sunburn protection during a critical growth phase of the tree.

“With CGW there’s a very specific time of emergence,” he said.

“Fruition Traps can confirm the time of emergence so the grower can have the product on, covering all the vulnerable surfaces – especially new growth – when the adults emerge.”

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