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The Japanese hop invasion
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State agricultural officials and environmental organizations are trying to stop Japanese hop, described as a rogue aggressive plant that is invading crop fields, roadside ditches, and streambanks in Southwest Wisconsin.

Agricultural producers, landowners, hunters, and anglers are being asked to keep an eye out for the invasive plant report any potential sightings to the authorities.

Japanese hop is a serious threat to crop production and water quality, as it can prevent the harvest of field crops, cause erosion that impairs the water quality of rivers and streams, and outcompete native plants that stabilize soil and create wildlife habitat.

This nuisance plant is a shallow-rooted vine that can climb over existing vegetation or structures to heights of 10 or more feet with the help of rough-textured stems covered with sharp spines. Its leaves typically have five to seven lobes. Japanese hop reproduces by seed, and can be spread by wind and water. Recent infestations are thought to have been spread during flood events, as well as by maintenance vehicles and agricultural equipment.

Japanese hop is now established in the Sanders Creek and Grant, Platte, and Castle Rock/Blue river watersheds in Grant County, Copper Creek watershed in Crawford County, the West Fork of the Kickapoo River watershed in Vernon County, and most recently in the Pine River watershed in Richland County. Any other suspected populations should be reported.

“We’re asking people to report Japanese hop, if they suspect they’ve seen it,” said Matt Krueger of the River Alliance of Wisconsin. “Early detection is critical with this plant, as once it is established, it’s very difficult to eradicate because an individual plant produces thousands of seeds. If we can catch infestations early, we stand a better chance of managing them.”

While physical and chemical controls can be effective at combating Japanese hop, landowners should not try to remove the plant on their own, or harvest and transport crops or hay off of sites infested with hop; the plant goes to seed in early fall, and attempted control efforts at this time could further worsen its spread.

For more information, or to report a suspected population of Japanese hop in southwestern Wisconsin, contact Krueger, (608) 257-2424 ext. 125, or Don Barrette at Southwest Badger RC&D, 348-7114.