Agent Orange!!! Live fast, die young and leave a withered corpse with no organs left to donate. That stuff is still killing people nearly a half century after some mook dreamed it up.
Supposedly it was a mixture of 2-4-D and 2-4-5-T, both of which could be had commercially by themselves during the 60's. Don't ask me the proportions; dont know. Also pretty sure that one of them has been discontinued from production and sales for some time. Some very old line Feed and Seed store located out in Back of Beyond County, State of Nowhere, might still have some in the furthest storage silo out in the back 40 but you better be on the lookout for snakes and bahb-wire on account of both them were out there too.
All this aside, manual labor is about the only way to guarantee you get the stuff and it will likely be a yearly exercise for quite a few years before you can declare it as being "ex-Kudzu".
Nick