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Can Pre-E treatment kill new grass growth from spring aeration?


LawnSite Senior Member
Chicago, IL
One of the benefits of aeration is to has new grass growth sprouting from the aeration holes. According the the Ryan brochure: 7-10 days after aeration, the holes will be filled with white actively growing roots. I am assuming that these roots with produce new grass growth. Will a Pre-Emergent (Dimension) kill the new grass growth, just like it would kill new grass seed growth?


LawnSite Bronze Member
South Bend, IN
Most pre-emergents in use today control grassy weed germination by stunting root growth. Weeds sprout, try to grow roots, are not successful with root growth, therefore they die right after germination. This chemical root stunting barrier is generally just in the top 1/4" of soil or less.

Pre-emergents do not hurt existing roots. BUT, if your grass plants try to grow NEW ROOTS FROM THE CROWN, which is a common way for grasses to grow, then it is also possible for pre-ems to inhibit new roots from existing crowns. While this is recognized by many experienced people in the business, manufacturers do not provide information on this aspect of pre-ems.

There are some concerned operators in the industry, mostly in southern golf courses, who worry quite a bit about harm to existing grass plant rooting. Instead of using standard pre-ems, some of them will apply siduron (which is specific to crabgrass and a few other grassy weeds) on a monthly basis; siduron is short lived and very expensive compared to standard pre-ems. Others will skip the pre-em and apply low rates of post emergent crabgrass control, like Acclaim, on a biweekly regimen.

So, yes, pre-ems can hurt grass roots, but just how much is a chemical company secret. You can only learn for yourself in your area by experimentation and observation.