Western Corn Rootworm Larvae

Larvae of western corn rootworm, Diabrotica virgifera virgifera, feeding upon corn roots. Credit: Image by Stephen Ausmus, USDA Agricultural Research Service

Study demonstrates how specific farming practices related to greater corn rootworm damage can have farther-reaching results.

A prowling hazard that has stymied United States corn growers for years is now returning to the leading edge: western corn rootworm. In some cases referred to as the “billion-dollar bug,” the types’ small larvae chew through the roots of corn plants, triggering devastating yield losses. In 2003, farmers started planting a genetically crafted range of corn referred to as “Bt,” which produces a protein harmful to the pest species– however by 2009, the billion-dollar bug had already developed adaptations for resistance to the toxic substance.

A brand-new research study suggests that slowing the revival of western corn rootworm may require a larger-scale technique than formerly thought. The findings, which were released in the Ecological Society of America’s journal Ecological Applications, show that when farmers do not follow best management practices for mitigating corn rootworm within a field, they also threaten surrounding fields.

Iowa Corn Field

Corn rows as far as the eye can see in Buchanan County, Iowa. Credit: Initial image from Carol M. Highsmith’s America, Library of Congress collection. Digitally enhanced by rawpixel.

Main author Coy St. Clair and his colleague Aaron Gassmann pinpointed 64 “problem fields” across Iowa, where western corn rootworm had caused greater-than-expected levels of injury to corn between 2009 and 2013 in 2 varieties of Bt maize: Cry3Bb1 and mCry3A. Compared to fields where rootworm had actually not harmed Bt maize, the issue fields had higher levels of constant maize growing in surrounding buffer areas.

Regular crop rotation is an essential strategy for interfering with rootworm’s life cycle: when rootworm eggs hatch in a field without corn, the larvae starve prior to they have a possibility to develop and lay eggs. Nevertheless, continuous planting of corn tends to be more successful in the short-term, leaving corn growers with tough decisions about how to handle dangers.

St. Clair, now a research study entomologist for Genective (Champaign, Ill.) who carried out the research study as a Ph.D. student at Iowa State University, says that the story of western corn rootworm resistance to Bt illustrates that pest mitigation is a shared duty.

Constant maize growing offers nascent rootworm populations a chance to evolve resistance to the Bt contaminant– and for those newly resistant offspring to take a trip to other fields.

” The takeaway here is that a farmer who is employing best management practices– such as frequent crop rotation, or planting of non-Bt maize– will efficiently manage rootworm and delay resistance in their own field firstly, while all at once helping to delay resistance advancement in surrounding populations secondly,” explained St. Clair. “On the other hand, a farmer who is planting numerous years of the very same trait will risk resistance in their own field, while contributing to the exhaustion of the shared resource of quality susceptibility.”

Since 2020, agronomists have verified that populations of western corn rootworm resistant to the 2 Bt traits examined in the research study exist across the US corn belt, together with 2 additional Bt qualities.

Recommendation: “Linking land usage patterns and bug break outs in Bt maize” by Coy R. St. Clair and Aaron J. Gassmann, 11 January 2021, Ecological Applications
DOI: 10.1002/ eap.2295

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