Bt Corn

Why does a Piedmont corn grower have to plant a 20% non-Bt refuge when an Iowa grower only needs 5%? The answer is corn earworm, the same insect that becomes cotton bollworm. It has already beaten most of the Bt proteins in our corn. Geoff and Glenn break down how refuge works, whether it's still doing its job, and what it means for your seed order. Why 20% here and 5% up north: Earworm feeds on corn, then moves to cotton and soybeans in the same season, and Bt isn't strong enough to kill it outright. The Corn Belt's 5% rule was built around European corn borer, which lives almost entirely on corn. How refuge actually works: Non-Bt corn produces susceptible moths that mate with rare resistant survivors, which keeps resistance genes diluted. That only works if the refuge is close by and planted at the same time as your Bt corn. The rules in the Carolinas: Every county in NC and SC counts as a cotton-growing area. Refuge-in-a-bag doesn't count here, so you need a separate 20% non-Bt block within half a mile. Where resistance stands: Earworm is now resistant to the older Cry proteins across the South. Vip3A still protects ears, but resistance genes are already showing up, and that same protein protects your neighbor's cotton. Does refuge cost you money?: NC State on-farm strip trials found no profit difference between a well-chosen non-Bt hybrid and 100% Bt corn. Hybrid choice mattered more than the trait. What's coming from EPA: Proposed changes, including requiring Southern growers to buy refuge seed along with their Bt seed, are still on the table but haven't been finalized.