I was talking to a guy in the landscape / horticulture field the other day. And we were discussing Pre-emergents. He was dead set against them (in favor of organic gardening, and no chemicals) and I was for them, having had very favorable experience with Pre-emergents like Cassaron and Snapshot. (Yes, I understand that Cassaron is a post-emergent too! Get off my back!) So as we were talking he said, matter of factly, "Pre-emergents are really a waste anyway. Because as soon as anyone sets one foot into the area where you've applied your pre-emergent, they've totally negated it's effectiveness." I'm not sure that's true. It seems to me that Pre-emergents work by changing something in the ground so that seeds won't germinate when they land in that area. Seems to me that once the ground is "sterilized" like this (for lack of a better term) then it should stay as such, regardless of whether someone walks there or not. But does anyone know for sure? Whose right? Him or me?