Fast-Growing Invasive Weed Identified in Iowa

Fast-Growing Invasive Weed Identified in Iowa
An eastern Asian weed found its way into Iowa this year. Mile-a-minute weed is invasive and has been found as far west as Indiana and Kentucky with one outlier in Oregon. This is the plant’s first appearance in Iowa.

Mile-a-minute weed is part of the smartweed (Polygonaceae) family and is a vine that can reach up to 20’ long. It can be identified by light green, triangular leaves; sharp, downward curing spines on the stem, petiole and main leaf veins; a saucer-shaped sheath that encircles the stem at the nodes; and round, iridescent blue fruit found mid-July until frost.

“Although this was my first encounter with mile-a-minute weed, it was easy to see why the plant is considered a threat,” said Bob Hartzler, Iowa State Extension weed scientist in a recent press release. “This infestation was less than a quarter acre in size, but it was crowding out existing vegetation. The weight of the plant was pulling down a stand of miscanthus, a species known for establishing monocultures.”

Although it’s just now identified, Iowa researchers say this weed has been present for at least five years, leading to a large seed bank. These seeds can survive in the soil for at least eight years. The weed excels in moist, sunny locations where plant materials, such as leaves or brush, are on the soil.

Just as with other invasive species, control could be challenging. It will take multiple application of herbicides during the growing season, and non-selective herbicides that kill other plants and leave bare spots could encourage new flushes of mile-a-minute weed. Hand-pulling is effective as the weed has a small root system, too.

The Forest Service is looking into biocontrol methods and has been since 1996. Iowa is not investigating a mile-a-minute specific weevil, which has been released in other states since 2004. Research shows the weevil’s success is tied to weather conditions.

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