How do you know if you're planting corn that has the refuge hybrid built in the bag? Nearly every company selling seed uses a different color of seed treatment on the two hybrids that go in the bag. If you look at the seed in the sack or later dig to check depth, you should find some seeds of both colors.
Recently, Brock Gutwein, Specialty Hybrids, dug up portion of a row and found both colors of kernels. The GMO hybrid will be found most often. The hybrid without traits acting as the refuge to help protect against insect resistance will be found, but much less often. If it's 5% refuge-in-a-bag, you should find 19 kernels of one color for every 380 kernels of the non-GMO hybrid of the other color.
Just because refuge-in-a-bag hybrids are here doesn't mean you can forget about complying with refuge requirements. Not all traited corn is refuge-in-a-bag. There are still hybrids sold that have above-ground control against corn borer and other insects, but not belowground control of rootworm larvae.
Jeff Phillips, Tippecanoe County Extension ag educator, recently planted a plot using one of those hybrids. The bag carried a tag explaining the refuge requirements since the refuge wasn't built in. In this case it can be accomplished by planting non-GMO corn elsewhere to satisfy the requirement. Most tags attached to bags spell out different options for meeting the refuge requirement. If not, your seedsman should be able to help you determine how to satisfy refuge requirements.
The bottom line is simple. If you plant hybrids that are refuge-in-a-bag, maintaining proper refuge is easy – so easy you can forget about it. If you're not planting refuge-in-a-bag hybrids, you still need to account for the refuge on your own.