Glyphosate sprayed on and with no rain for several hours will kill it.
the commercial version is often branded Gallop or Rosate and it much stronger than the retail versionI use a product called roundup concentrate which i believe is the same as Glyphosate, just branded and also i think a lot more expensive - but i got a few 1L concentrate a few years ago, on offer around £30 a litre , works really well , allow about 10days for the thing to die back, i have cleared loads of ivy and weeds , under llyandi and also in out courtyard - excellent stuff, use it a few times a year around different places
I'm not sure it is actually more concentrated, but you can buy it in 5-10L (maybe bigger) bottles. Regular Roundup seems to be 20ml/L for normal use and 20-30 seems to be the standard for every product I've bought (double for scorched earth policy and more established shrubs) and they all seem to work as effectively.the commercial version is often branded Gallop or Rosate and it much stronger than the retail version
30ml per litre in a sprayer
Are you sure this is not Japaneses knotweed . Red branches are a sure sign
If so you would need it commercially treated