Growers face battle against herbicide resistance

It takes a few ounces per acre of a herbicide containing glyphosate to kill the weed downy brome. At least, it’s supposed to.But when a farmer sent a sample of the weed to Washington State University professor Ian Burke’s lab, researchers determined it would take seven times the maximum label rate of the herbicide to kill it.That’s an extreme example of a problem that’s become more serious in recent years: herbicide resistance in weeds. For decades, farmers have relied on an array of herbicides to get rid of weeds that compete with their crops and drastically reduce yields. Now, through repeated use of those chemicals, the weeds are developing resistance to them.