Research shows that individual farming practices associated with greater damage to the corn root worm may have broader effects.
A hidden threat that has stifled U.S. corn growers for decades is now back in the forefront: western corn has taken root. Small larvae of what is sometimes called the “billion dollar beetle” cause crop losses by chewing and destroying the roots of corn plants. In 2003, farmers began planting a genetically engineered variety of corn known as Bt, which produces a protein that is toxic to pests, but by 2009 had developed adaptations to resist billions of dollars of insect toxin.
A new study suggests that slowing the recovery of the western corn root worm may require a larger-scale strategy than previously thought. The study was published in the journal of the American Environmental Society Environmental Applications, show that when farmers do not follow best management practices to reduce corn root worms in the field, they also endanger the surrounding fields.
The main author is Coy St. Clair and colleague Aaron Gassmann identified 64 “problem areas” across Iowa where western corn root worm caused more damage than expected for two varieties of Bt corn in 2009-2013: Cry3Bb1 and mCry3A. Problem areas had higher levels of sustainable corn cultivation in the surrounding buffer areas compared to areas where root rot did not damage Bt corn.
Regular planting rotation is the main strategy to interfere with the root worm’s life cycle: when the root worm eggs hatch in a non-corn field, the larvae go hungry before they have a chance to grow and lay eggs. However, sustainable corn cultivation tends to be more profitable in the short term, making it difficult for corn growers to make decisions about how to manage risks.
St. Clair is a research entomologist for Genective (Champaign, Ill.), Who is currently conducting her doctoral research. A student at Iowa State University says the story of resistance to the corn root worm in the west shows that pest reduction is a shared responsibility. “If the pest remains sensitive, everyone benefits. If resistance develops, everyone suffers. ”
Sustainable corn cultivation provides an opportunity for emerging root worm populations to develop resistance to Bt toxin and for new generations to travel to other areas.
“The choice here will effectively manage the root worm of a farmer who uses best management practices, such as frequent crop rotation or non-Bt corn planting, while helping to delay resistance in their fields in the first place while the latter in surrounding populations,” explains St. Clair. “On the contrary, a farmer who cultivates the same trait for several years will run the risk of resistance in his field while helping to deplete the shared source of sensitivity to his traits.”
As of 2020, agronomists have confirmed the presence of two additional Bt traits in the U.S. corn belt of populations of resistant western corn root worms that are resistant to the two Bt traits studied in the study.
Reference: Coy R. St. Clair and Aaron J. Gassmann, “Patterns of land use in Bt corn and linking pests,” January 11, 2021, Environmental Applications.
DOI: 10.1002 / eap.2295