US farmers face plague of pests as global heating raises soil temperatures

Milder winters could threaten crop yields as plant-eating insects spread northwards and become more voracious, researchers say

Agricultural pests that devour key food crops are advancing northwards in the US and becoming more widespread as the climate hots up, new research warns.

The corn earworm (Helicoverpa zea) is considered to be among the most common farm pests in the US, ravaging crops such as maize, cotton, soya and other vegetables. It spends winter underground and is not known to survive in states beyond a latitude of 40 degrees north (which runs from northern California through the midwest to New Jersey), but that is changing as soils warm and it spreads to new areas, according to research led by North Carolina State University.