Bt Corn and Refuge: Smart Planting for Long-Term Success

Jun 23, 2025

By Dominic Reisig

Article by Alexis Alsdorf, NC State Department of Entomology and Plant Pathology PhD student

Helicoverpa zea (corn earworm or bollworm) is a common pest that feeds on many crops, including corn and cotton, across the United States. Over time, this pest has become resistant to some of the Bt corn and cotton traits that are supposed to kill it. To slow down this resistance, Bt corn growers in the southern US are required to plant at least 20% non-Bt corn, called a “refuge.” This refuge helps keep some earworms from becoming resistant to Bt corn. But many growers don’t plant this refuge because they worry non-Bt corn won’t yield as well as Bt corn.

To answer this question, we did a study over two years (2022 and 2023) on grower fields in North Carolina. We tested different corn hybrids, some with Bt traits and some without. The growers planted and harvested the corn using their usual equipment and timing. We checked the fields when the corn was almost ready to harvest to see how much damage the corn earworm caused and how much corn was produced.

Source : ncsu.edu

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