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Crabgrass Killer

Discussion in 'Pesticide & Herbicide Application' started by D-Man, Feb 6, 2001.

  1. KirbysLawn

    KirbysLawn Millenium Member
    Posts: 3,486

    Could you elaborate on which part of the post is incorrect and give us guidance on the correct information?
  2. Jim explained it all in his post why this is a bad practice.

    Mscotrid wrote:

    >You would be better off to get your seed in the ground as early as possible and after germination come back in with Dimension.

    1.If you apply this product when the turf is new you will stress the plant while it should be building up reserves for the summer sress to come.

    2.Buy not applying Tupersan at time of seeding the the turf has to compete with all the weeds that will germinate.

    3.If you do not apply tapersan the lawn won't be as thick do to weeds and the customer will demand you kill the weeds.
    This is a callback and results in lost income.

    The above applys to commercial and residential turf.
    When it comes to sports fields I treat the fall sports fields in the spring in a completely different fashion.
  3. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    If you have never seen the effect of root inhibiting pre-emergents on grass roots, here is a sample.


    The plants on the left received no pre-em; those on the right received pre-em after germination. ( larger image ) These are crabgrass plants dug up early July; germ here is usually around mid-late May. The poor guy at lower right had one root below the limits of pre-em barrier, and that was the only decent root. Roots on all plants dug up that had received pre-em after germination were just stubs - can see it in enlargement in plant upper right.

    Now, since new roots of desireable grasses grow from the crown, which is above the pre-em barrier, the use of pre-em will inhibit new root growth in your desireable grasses. To my knowledge, the only pre-ems that will not have this effect are Ronstar and siduron. I have gone out with another operator on his lawns, and told him which ones had pre-em and which did not, just by looking at rooting in each lawn. Roots views are obtained using a cup cutter; try to get a 6" deep sample.

    In the case of a newly seeded lawn, application of a pre-em - other than siduron or Ronstar - sooner than a year after seeding is going to reduce the vitality of the turf by reducing root growth. (IMHO)

    Wish I had taken pictures of Dr W's lawn. This was a 23K lawn sodded in Dec. Had pre-em for 4 years, and lawn was riddled with patch disease, dollar spot, and red thread all that time. All this time, there was absolutely no root growth into the soil - we attributed that to the extremely poor soil. In 5th yr, Dr W wanted to overseed, so pre-em was not applied. In mid-March of 6th year, roots had grown to 3"-4" deep; By mid-April, roots were 6"-8" deep. The only difference was that pre-em had not been applied.

    For a production oriented operation, pre-em is a good thing, because you can rack up the apps with minimal fuss from clients. When disease or other pests harm the turf, they can be blamed on the disease, insect or other problem, and more $$$ can be churned. If you are challenged to grow a really healthy lawn, you will use a heck of a lot less pesticide, and your clients will pay more for your time involved in performing an intelligent, responsible service.

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