WASHINGTON (AP) — The Agriculture Department has approved the use of genetically modified corn and soybean seeds that are resistant to a popular weed killer.

However, farmers won’t be able to take full advantage of the seeds until the Environmental Protection Agency issues a second ruling allowing the use of Enlist, a new version of the 2,4-D weed killer that’s been around since the 1940s. The EPA has said it will rule this fall on Dow AgroSciences’ application to market the chemical.