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Hybrid swarm may create global crop mega-pest

Commonwealth Scientific & Industrial Research Orgaization Helicoverapa armigera
Globalization and increased movement between countries and continents means movement of agricultural pests is becoming more common. Global trade means global pests.
Hybridization of cotton bollworm and corn earworm confirmed in Brazil.

Researchers in Australia have confirmed the hybridization of two of the world's major crop pest species into a new "mega-pest," according to Australia's Commonwealth Scientific & Industrial Research Organization (CSIRO).

One of the pests — cotton bollworm — is widespread in Africa, Asia and Europe and causes damage to more than 100 crops, including corn, cotton, tomatoes and soybeans. Cotton bollworm is extremely mobile and has developed resistance to all pesticides used against it, CSIRO said. The cost of the pests' damage and control runs billions of dollars a year.

The other pest — corn earworm — is a native of the Americas and has a comparatively limited resistance and host range, CSIRO noted.

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

CSIRO researchers, in a paper published in Proceedings of the National Academy of Sciences of the USA, provides clear evidence of the hybridization of the two moths in Brazil.

"A hybrid such as this could go completely undetected should it invade another country," said Dr. Paul De Barro, research director of CSIRO's Biosecurity Risk Evaluation & Preparedness Program.

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," CSIRO scientist Dr. Tom Walsh said.

According to CSIRO, a concerning finding among the Brazilian hybrids was that one was 51% earworm but included a known resistance gene from the bollworm.

Lead author of the paper Dr. Craig Anderson, a former CSIRO scientist now based at The University of Edinburgh in Scotland, believes the hybrid study has wide-ranging implications for the agricultural community across the Americas.

"On top of the impact already felt in South America, recent estimates that 65% of the U.S.'s agricultural output is at risk of being affected by the bollworm demonstrates that this work has the potential to instigate changes to research priorities that will have direct ramifications for the people of America, through the food on their tables to the clothes on their backs," Anderson said.

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