Here is some information I have on file. Be sure to check out the last paragraph as it appears there may be some resources out there to help :)

Japanese knotweed (Fallopia japonica) is an aggressive perennial that reproduces both by rhizomes (underground stems) and by seed. It is often found in shaded to partially shaded habitats on moist, nutrient-rich soils, though it can thrive in gardens and on roadsides as well.

Physical control.

Repeated chopping or digging may eventually deplete underground reserves thus reducing the competitive edge of Japanese knotweed, however it is expected to take several growing seasons to achieve eradication. Both root and stem fragments can root and result in new plants, therefore any plant material removed for control should be placed in the trash headed to the landfill and not in yard waste or compost. Mulching is not an effective means of suppressing Japanese knotweed. Mowing is not recommended as it can spread the infestation.

Biological control.

At MSU Dr. Marianna Szucs laboratory group is working on a testing a biological control agent for Japanese knotweed, however this is still in the preliminary stages of testing for the state. More information Dr. Szucs program can be found at http://mariannaszucs.weebly.com/ in the Resources section.

Chemical control.

Repeated herbicide applications of glyphosate or various brush killers, such as triclopyr (Garlon, Pathfinder, Brush-B-Gon) or triclopyr + 2,4-D (Crossbow) should help keep this plant under control, but eradication is difficult. Chemical applications can be made to cut stems for more effective treatment of small populations, see herbicide labels for details. Glyphosate (e.g. Roundup Weed and Grass Killer concentrate) is usually the best choice for homeowners because of its safety, ease of application and lack of residual activity in the soil, however, in a lawn triclopyr or triclopyr + 2.4-D are better options because they will not harm the grass. Be sure to read and follow all labeled instructions. Repeat applications will likely be necessary.

There are more potent herbicides available that may provide eradication, but they are very persistent and can impact trees and shrubs with roots in the area. If you would like more information on these herbicides please contact me via email at <personal data hidden>.

**Note, if the neighboring properties also have this weed and they are not actively controlling it; it will continue to be a problem.

It looks like your local Cooperative Invasive Species Management Area (CISMA) might also be able to help as they have some information about Japanese knotweed listed on their site and it says, "For invasive plant treatment assistance contact the West Michigan CISMA Coordinator at 616.402.9608 or email <personal data hidden>" They may have some resources available to help you, so it might be worth a call/email!

https://wmconservation.net/