Australian scientists have found evidence that two of the world's most damaging pests have hybridized to create a dangerous mega-pest with pesticide-resistant genes. The new hybrid has presently only been identified in Brazil but the researchers warn that its spread throughout the global agricultural community could be devastating.

Helicoverpa armigera, commonly known as the cotton bollworm, and Helicoverpa zea, the corn earworm, are two types of very hungry caterpillar that cause billions of dollars of damage to crops every year. Corn, cotton, tomato and soybean are just some of the many crops these pests can attack, with the cotton bollworm having developed resistance to all pesticides targeted at it.

In 2017, an eight-year project that mapped the entire genome of both caterpillars was completed. The study was designed to help researchers identify specific genes that cause the pests to become resistant to pesticides. A new paper has now been published showing evidence that the two moths are clearly hybridizing in a variety of novel ways.

"No two hybrids were the same suggesting a 'hybrid swarm' where multiple versions of different hybrids can be present within one population," says one of the researchers on the study, Tom Walsh.

The researchers suggest that it is too early to identify signs of successful selection in the resulting hybrids but the clear variety of genetic transference found between the two individual pests is a source of great concern. The impact of these evolving pests is already damaging agricultural output in Brazil, and the researchers warn that if these mega-pests establish as a discrete species it would be agriculturally problematic for the entire Americas and beyond.

"They are very impressive little things," Walsh told the ABC. "They can eat a wide range of hosts, seem to survive all our attempts to control them … and that really is my research interest: why isn't it dead when it ought to be?"

The research was published in the journal PNAS.

Source: CSIRO

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