Agronomists are warning that Palmer amaranth, a weed once confined to the South, is becoming more pervasive in Iowa and other Midwestern states.

The prolific weed was first found in Iowa in 2013, and its presence has been officially confirmed in five counties — two in southeast Iowa and three in southwest Iowa. However, agronomists believe it is present in much more of the state.

"While we hoped that the few infestations scattered across Iowa could be contained, unfortunately a few weeks ago I found out...