Does wetness affect weed killer/preventer?

Discussion in 'Homeowner Assistance Forum' started by A72CUTLAS, Mar 27, 2007.

  1. A72CUTLAS

    A72CUTLAS LawnSite Member
    Messages: 38

    I bought some Scott's Halt while at HD(was intending to get the Lesco's w/Potash but I have a Koi pond and the label advised against using it near fish). Anyway, when I bought it the weather was dry but since it's rained 2 days straight. How soon after the rain can I put down weed killer/Pre-em? The label says the grass should be dry, but remains effective if it storms after app. If this is the case why does it have to be dry when you first apply it?
    Just another n00b question. Thanks for your patience.
  2. Rtom45

    Rtom45 LawnSite Senior Member
    Messages: 456

    Pre emergents work by forming a barrier on the soil surface. If you apply the product when the lawn is wet, it will stick to the grass and not make contact with the soil. If it rains after the product is applied to a dry lawn it has already made soil contact so the rain won't hurt it. The only exception may be a gully washer that carries the pre m out of the lawn.

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