I'm spraying simazine out of my Z-spray at 1/3 gal per 1000. At 1oz per 1000. mixed with threeway ester. I sprayed this mix four weeks ago and it rained two weeks ago with about one inch of rain. I'm trying to kill poa. I can't tell if it is working yet. how long does it take to work. or do I need to do one more treatment. I have some yards with poa and trying to take care of it now. I did use prodiamine full rate in Sept.