Roundup is toxic and bad for the environment, humans and pets. The vinegar spray is fine, but the guy form Massey suggested a weed torch. No bending, works great. Available at Lowe's ($50) or on Amazon ($25). Guess where I bought mine..
Weed Torch on Amazon
You will also need a $5 can of propane which is cheaper locally due to the cost of shipping hazardous materials.