I've known John Boyd for a long time. He lives in central AR and works out of the Little Rock extension office. He's a great weed scientist. His recommendations aren't necessarily wrong, but I do notice a lot of simazine recommendatiosn coming out of his office. Maybe it's b/c simazine is so cheap and has both PRE and POST activity tht he recommends it to LCOs as a simple 2-for-1 product, but I just don't see the control out of it that I would like. Besides, the label restrictions make it hard for me to use it. Wilson, I will find you some better references shortly, but this article (written by Fred Yelverton of NCSU) talks abotu Poa germinating in late summer: http://grounds-mag.com/mag/grounds_maintenance_control_winter_weeds/ NCSU recommends PRE for Poa should be applied no later than Sept 15 for most of NC. I would certainly agree. PRE needs to be down before germination in order to work. Remember, germination is NOT emergence -- germination usually happens weeks or months before you can see it.