Wetland Delineation Act of 2018 This bill modifies wetland conservation requirements that deny various Department of Agriculture (USDA) program benefits to agricultural producers who plant crops on certain converted wetlands. The bill requires USDA to (1) determine that an exemption permitted under current law does not apply to a producer before determining that a producer is ineligible for benefits, and (2) publish categorical minimal effect exemptions within 180 days of the enactment of this bill. The bill also authorizes additional funding for the wetland mitigation banking program.