The visible part of Japanese Knotweed dies back every winter. Most of Knotweed in my area is now dead or dying but it will return in the spring.
It is now probably too late to treat your Knotweed this year. If you have a problem with Knotweed I would be very happy to talk to you but there is very little I can do until next year’s growing season.
It is possible to dig out the root system over the winter but it is not a service I can offer. However, I can arrange for another company to quote for this sort of work.