Blame demand exceeding supply for the shortage of Rely 280, a contact herbicide from Bayer CropScience, Research Triangle Park, N.C.

In fact, the product, which contains the active ingredient glufosinate, will not be available in the U.S. specialty crop market for the 2013 season, says Nevada Smith, product manager.

"The issue is with global demand increasing with corn and soybeans and seed-trait technology," he says. "There was no way to forecast around that. We're focusing on getting the product back on the market as soon as possible."

Many growers in recent years have turned to glufosinate to help control glyphosate-resistant weeds, since glufosinate has a different mode of action.

In the corn, soybean and cotton markets, glufosinate is marketed as Liberty and is part of the Liberty Link system.

Growers planting Liberty Link corn hybrids, for example, can apply the herbicide over the top of the crop without injury. It kills the weeds but not the crop.