LINCOLN, Neb. (AP) _ Growing seed corn is already big business in Nebraska, and several of the big seed companies are expanding their operations in the state. On the research end, lab technicians can splice together genes that give kernels genetic resistance to corn borers and rootworms. That gives the crop tolerance to the herbicides that wipe out invading weeds. But the high-tech work of seed development still relies on a month of hard labor from teenagers who detassel corn each summer. Bill Sloup, a Seward teacher and detasseling veteran, keeps hearing how companies are going to find the answer that allows seed corn to grow sterile, but he's been hearing that for 30 years. Pioneer's Jeff Dilbeck says the seed companies will likely continue needing detasselers for many years to come. And the number of detasselers needed in Nebraska may grow because two seed companies are expanding. Monsanto is building a new processing plant between Utica and Waco. And Pioneer is spending $13 million to upgrade a similar plant near York.