Glyphosate is the way to go. REMEMBER!!!!! do not use over the recommended rates when using glyphosate... You will put the plant in shock and it will not take the herbicide down to the root and you will treat again this or next season. So many people try to overdue it and end up making more work for yourself. More is less in this case.!!! The leaf has a waxy coating that needs to be burned through with a surfactant. Do not use dish soap use an aquatic surfactant like Cide-kick. If you need help with a rate let me know.