Clearfield corn has resistance, or tolerance, to ALS-inhibiting herbicides such as Lightning and Pursuit. Very little, if any, Clearfield corn will be sold in 2008. In several years, DuPont plans to release Optimum GAT corn, which will have resistance to ALS-inhibiting herbicides and to glyphosate herbicide.
For more information on this or other topics related to corn production, contact your state extension corn specialist or your local extension educator/agent.
Here is the link to the corn extension specialists: state extension corn specialist.