US farmers face a plague of pests as global warming raises soil temperatures

Agricultural pests that devour major food crops are moving north across the United States and spreading as the climate warms, new research shows.

Corn earworm (Helicoverpa zea) is considered one of the most common agricultural pests in the United States, ravaging crops such as corn, cotton, soybeans, and other vegetables. It overwinters underground and is not known to survive in states beyond 40 degrees north latitude (which extends from northern California through the Midwest to New Jersey), but it changes as soils warm and spread to new areas, research shows. run by North Carolina State University.

The report follows research from the University of Washington in 2018 which found that a warming of 2°C (3.6°F) would increase the number and appetite of insects around the world, causing them to destroy 50% more wheat and 30% more corn than they currently do. Rising heat stress is already affecting yields, with staple crop harvests in Europe declining this year due to heat waves and drought.

Pest outbreaks have serious implications for food security. “As the climate changes, wintering areas are likely to shift north,” said co-author Anders Huseth, an entomologist at North Carolina State University. “It’s the canary in the coal mine for agricultural pests.

“Making sense of what is happening with [the corn earworm] is really important for agricultural producers. Other pests that could spread north into the United States in the same way include fall armyworm, green clover worm, soybean looper, and velvet bean caterpillar.

The researchers created maps that showed three distinct geographic areas across the United States – the “southern range” where corn earworms survive the winter, a “transition zone” where they can survive winter and the “northern limits”, where they are generally unable to survive the winter because soil temperatures drop below freezing.

Researchers already knew that warmer winter soils meant insects that live in the soil were more likely to survive. Using four decades of soil temperatures and corn earworm monitoring data, the researchers predicted the future distribution of the pests.

The Southern Range has grown 3% since 1981 and is expected to double in size by the end of the century as other areas shrink, according to the article published in Proceedings of the National Academy of Sciences. Corn earworm borers can disperse up to 1,000 km using seasonal winds, which means they can spread quickly if the conditions are right.

Over the next several decades, the model shows that this insect could expand its wintering range into the U.S. Corn Belt in Ohio, Indiana, Illinois, Missouri, and Iowa. In Minnesota, for example, no corn earworms survived its harsh winters, but models suggest the entire state will be in the transition zone by the end of the century.

This could lead to increased use of pesticides and lower yields. “If intensive corn production does not also move north with climate change, we expect corn earworm to become a more frequent and significant problem in these states,” the official said. Dr. Douglas Lawton, former postdoctoral researcher at North Carolina State University and co-author of the paper.

“Organic growers have a major challenge controlling this pest and often accept significant crop losses when infestations are high,” he said.

Monitoring soil temperatures could help predict the spread of pests, helping farmers control them more effectively, the report suggests. Huseth said, “We would like to come up with a better forecasting tool for this pest, as well as a risk prediction model, to give growers better information about the spread of the pest. Success here could reduce both costs to farmers and pesticides to the environment. »

US farmers face a plague of pests as global warming raises soil temperatures

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