Hi Barry, thank you for taking the time to provide this feedback. Since the material we use is systemic, it is intended to kill the weed out at the root first, prior to burning up the top. Because of this, it can take 7-10 days this time of year after the application for the weeds to die out. If after that time frame the weeds have not died out, we have a 6 month warranty on our service. Please let us know if that is the case, but I am confident the material just needs to time to work. Thank you!