The science behind dropping the refuge is that there are now three genes for rootworm control (one from the VT3, two from the Herculex Extra) and two genes for corn borer (one from the VT3 and one from the Hrculex Extra) and therefor the likelihood of resistance developing is less due to more modes of action. In other words, consider it like weed control. If I have a giant ragweeds and I spray it only with 2-4D, they chance of it becoming resistant is better than if I spray them with 2-4D and Roundup. Two different modes of action at work.