Winterkilled alfalfa fields have unexpectedly been found in two southwestern Wisconsin counties, and the affected area extends into northwestern Illinois and northeastern Iowa, reports Dan Undersander, University of Wisconsin extension forage agronomist. In Wisconsin, the problem apparently is limited to southern Grant and Lafayette counties, says Undersander. Fields farther north are starting to green up, and no further damage had been reported as of Monday. “The question is, how far did it go into Illinois and Iowa, and that’s what we’re trying to get some answers on,” he says.

In the two Wisconsin counties, some whole fields are dead and others are so badly damaged that “it’s 100% loss even if it wasn’t 100% kill,” says Undersander. Although older alfalfa stands are most susceptible to winter damage, “we’re seeing all ages of stand killed in the region.”

He believes cold weather was the cause. The affected area had sufficient snowfall to insulate the dormant crop, but some of it melted. “I suspect the snow wasn’t as deep as some people thought it was across these fields,” says Undersander. “The other thing is, particularly some of the last snows were pretty wet and slushy, and they don’t insulate very well.”

He says affected plants have soft, mushy taproots just below their crowns. Some may begin to green up and then die. Plants that put out second leaves likely are unaffected.

For Undersander’s recommendations on reseeding or replacing winterkilled alfalfa, go to hayandforage.com.