Pest resistance threatens corn industry’s newest biotech defense, study warns

The corn root verses, the parasites responsible for billions of dollars in losses of annual crops, evolve a resistance which even weakens the latest biotechnology controls, according to a new study published in the journal Proceedings of the National Academy of Sciences.

Based on decades of data in several states, entomologists of the University of Arizona have found that the resistance advanced on the ground at Bacillus thuringiensis, or BT, undermines the effectiveness of the corn which targets worms with the combination of BT and RNA interference, or RNAI, a new biotech control that is the subject of joint instructions Radio.

The research team has analyzed the important data on the field collected in the past two decades in 12 previous studies, including millions of worms evaluated through the corn belt, which extends from west of Ohio to the east of Nebraska and northeast of Kansas.

“The results systematically show that in the fields where BT resistance has evolved, the combination of BT interference and RNA offers less protection against root worms damage,” said Bruce Tabashnik, principal of the study and head of the U of Entomology Department.

“These are not laboratory data,” he added. “These are real field data collected from university research and industry in several states.”

Scartigles Billion

The corn root worms are called “$ 1 billion bugs” for a good reason, according to Tabashnik.

“These are really harmful and insidious pests,” he said. “For each of the last two years, Rootworms has caused around $ 2 billion in return on corn in the United States, and there is another billion dollars that is invested each year to control them.”

Hidden underground, these coachery larvae gnaw at the blood of the life of the most precious culture in America. In the arms race against these pests, genetically modified crops have been an important tool, increasing yields while reducing farmers’ dependence on broad spectrum insecticides that can be harmful to people and the environment.

BT corn is designed to produce proteins from the soil bacteria that kill pests but are not toxic to humans or fauna, said Tabashnik. BT Corn Cibting Rootworms was introduced for the first time in 2003.

“It was very effective,” he said, “but after several years, an advanced resistance on the ground began to emerge.”

Too good

BT resistance comes from Darwinian selection, the same process that produces antibiotic resistance. Because the BT corn was so good to beat the backwards of rear corn root, many producers began to plant it year after year, according to Yves Carrière, co-author and study teacher in the Entomology Department.

Although it has erased most pests, some of them who were naturally, genetically less sensitive have inevitably survived and transmitted their resistance to the next generation.

The seed companies responded with the “pyramid” strategy, combining two different BT proteins to kill the same pest.

“The idea is that if the insect is resistant to a BT protein, the other will kill it,” said Tabashnik. “And that helped. But shortly after, the root worms have evolved a resistance to the two types of BT protein.”

A new defense line occurred in 2022, with the marketing of Arni. It works by “silencing” specific genes in the pest, essentially to stop the functions that the insect needs to survive. Unlike insecticides with broad spectrum, the ARNI targets a gene specific to a pest but not present in humans, animals or beneficial insects.

The use of the Arni against the corn root worms is the first application of this technology to control a crop pest. It kills more slowly than BT and is used in transgenic corn only with BT.

“He was never supposed to stand alone. He had to be a punch with BT,” said Tabashnik. “But when the Arni was really marketed, the efficiency of BT Plus RNAI has already been undermined due to the pre -existing resistance to BT.”

Losing the advantage of biotechnology

The results are worrying, according to the research team, as they highlight the risk that even this latest technology was losing its bite against corn parasites. Researchers advise to use integrated strategies to combat pests, including secular practices such as crop rotation, as well as planting “refuges” of conventional maize alongside transgenic crops to allow survival and resistance to the deadlines of ravages susceptible.

“Farmers are counting on this new technology in the hope that it would last for many years. Our study shows that the lifespan of this tool could be much shorter unless the management of resistance is taken seriously,” said Tabashnik.

“It is a reminder that there is no miracle solution. The evolution does not stop. Rootworms adapt, and if we do not diversify our approaches, we will continue to chase our tails.”