Danger of South American “mega-pest” hybrid migrating to Asia Pacific

By Lester Wan

- Last updated on GMT

Australia-based scientists have confirmed the hybridisation of two of the world’s major crop pests into a “mega-hybrid” pest. ©CSIRO
Australia-based scientists have confirmed the hybridisation of two of the world’s major crop pests into a “mega-hybrid” pest. ©CSIRO
There is a risk of a recently-discovered “mega-pest” hybrid migrating to Asia Pacific and destroying crops and disrupting the food chain, according to Australia-based scientists.

The Commonwealth Scientific and Industrial Research Organisation​ (CSIRO) scientists have confirmed the hybridisation of two of the world’s major crop pests — both moth species — into a “new and improved”​ pest.

One of them, the cotton bollworm (Helicoverpa armigera​), is widespread in Asia, Africa and Europe. It causes damage to over 100 types of crop including corn, cotton, tomato and soybean.

The cost of the damage and to control it amounts to billions of dollars per year.

The cotton bollworm is extremely mobile and has developed resistance to all pesticides used against it.

The corn earworm (Helicoverpa zea​), meanwhile, is a native of the Americas and has comparatively limited resistance and host range.

Danger of migration

However, the combination of the two in Brazil — in a novel hybrid with unlimited geographical boundaries — is a major cause for concern to Asia Pacific.

Dr Tom Walsh, senior research scientist of CSIRO, said the movement of insect pests is increasingly recognised as a major threat to food security, and is happening a lot.

As an example, a recent issue for Asia and Australia is the arrival of Spodoptera frugiperda​ (fall armyworm) in Africa.

“In just a couple of years, it has spread through sub-Saharan Africa, and will likely be heading to Asia next,”​ said Dr Walsh.

In terms of the new mega-hybrid entering into Australia, he said there are two routes: by natural movement from the North or through trade and movement of people.

“We currently have a project to look at both these routes (for the pest) into Australia,” ​he said.

“A hybrid such as this could go completely undetected should it invade another country,”​ added Dr Paul De Barro, research director of CSIRO’s Biosecurity Risk Evaluation and Preparedness Programme.

“It is critical that we look beyond our own backyard to help fortify Australia’s defence and response to biosecurity threats.”

While a combination of insecticides currently controls these pests well in Australia, CSIRO stated that is important to study the pests themselves for sustainable long-term management, worldwide.

Dr Walsh added: “With the amount of commodities coming from South America into Asia, I would be very surprised if there wasn’t a risk (to the region).”

“The key finding from our work is that it is very hard to identify these individuals as they look like species that are already in Asia. The only way you can tell is by sequencing the whole genome.”

Super hybrid swarms

The scientists confirmed that among the group of caterpillars studied, every individual was a hybrid.

“No two hybrids were the same, suggesting a ‘hybrid swarm’ where multiple versions of different hybrids can be present within one population,”​ said Dr Walsh.

He explained that the term “hybrid swarm” describes a situation when two previously isolated species or populations mix and where “all possible combinations” are still possible.

“This is what we see: no hybrid individual was the same. So we are at an early stage of the mixing event; the consequences of which are hard to predict,” ​he said.

A further implication or major problem is the development of resistance.

“The major issue is that you no longer know what you are looking at,”​ said Dr Walsh.

“It used to be that you could say if it was one species or the other based on morphology, crop type and geography. This is not possible anymore with these two species in the New World.”

Protecting Asia Pacific

Dr Walsh said surveillance would be crucial to understanding the risk and routes of incursion.

“In this case, we had to sequence the genome to identify these hybrid individuals,”​ he said.

“A useful thing to do would be to examine some of the major trading hubs for Asia to see whether this sort of thing is happening.

“Also, a focus on potentially higher-risk commodities where freshness and speed is key, such as cut flowers, fruits and vegetables."

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