crabgrass pre-m and root growth.

Discussion in 'Pesticide & Herbicide Application' started by locutus, Nov 29, 2004.

  1. locutus

    locutus LawnSite Bronze Member
    from NC
    Messages: 1,266

    Does an early spring application of crabgrass pre-emergent effect root growth of new lawn sewn in early fall. Lawn is up and green, though I suspect that the roots will be continuing to grow for a while yet. Thanks.
  2. upidstay

    upidstay LawnSite Bronze Member
    from CT
    Messages: 1,564

    If the lawn is nice and strong, then maybe, but I wouldn't do a pre-m unles it really came in great. And YES, it can affect root growth. My motto is, "When in doubt, don't". Wait a little and do some Drive later in the season. You can pre-m fauirly late into the season
  3. grassguy_

    grassguy_ LawnSite Senior Member
    from Ohio
    Messages: 633

    Since you are in NC I would consider using the early spring to continue to turf build with such as a starter fertilizer then return later in the spring with a treatment of dimension (pre-emergent) for control on crabgrass that will also work post emergent on early stage crabgrass. This is all assuming the lawn is well established into late spring, if not then use Drive as a post emergent for control on the crabgrass through late spring into early summer until lawn as buil a healthy stand.
  4. Bensulide ( betasan) will have the least effect on root prunning of labeled pre emerge on residential turf! The next best I believe is barricade followed by dimension!

    I believe hammons research this! guess hamons or tremor will confirm if I'm correct!
  5. YardPro

    YardPro LawnSite Gold Member
    Messages: 3,570

    not on established turf.

    mosts pre m's work by being absorbed in through the adventitious root from a seed, or piece of a rhizome or tuber.

    the chemical is absorbed, then in one way or another it affects the metabolism of the plant.

    since so little chemical is able to be absorbed, it cannot kill a large amount of material since there will be more cells, more chloroplasts, etc.

    on plants/grass with alot of biomass, it is like shooting giant with a BB gun.

    that's why pre M is not effectice once the plant is grown.
  6. Yardpro,
    been a hard 2 days chasing leaves, my muscles are sore, and maybe my mind is a little furry, but when you say not on established turf, are you referring to established crab or goosegrass?
  7. YardPro

    YardPro LawnSite Gold Member
    Messages: 3,570


    established turf

    pre M though does not work on any established weed.
    Dimension has some post emergent qualities, but only if you apply before the weed reached the third leaf etc.
  8. GroundKprs

    GroundKprs LawnSite Bronze Member
    Messages: 1,969

    Most all pre-ems are labelled for use on established turfgrasses - some labels will say well established. I work in cool season turf, and do not consider a fall seeding to be well established for at least a year and a half. Accordingly, any of my fall seeded lawns that need pre-em will only get siduron (brand name: Tupersan, and others).

    All pre-ems - except siduron - are root inhibitors. So over the long term, pre-ems likely prevent new root growth from the crown of desireable turf plants. I once had a lawn that had been sodded in December, and treated by a large lawn care company for a year. I worked on this lawn for several years, and could never get any decent root growth. The lawn was hammered by disease, especially summer patch, because of the poor rooting. Because summer patch here runs a 5 year cycle, the client wanted to overseed the fifth year, so no pre-ems were applied. The next spring (2 years after last pre-em application) the grass started growing a fabulous root system. What happened here? The sod was put in so late, no root growth was able to happen before winter. Big LCO made late winter app of pre-em, so new root growth was stubbed off. And subsequent years of pre-em apps prevented any root growth. (There is such a heavy residual of pre-ems, it has been found that if you use the same pre-em product for 3 years on a lawn, you only need to apply at half rate after 3rd year for full efficacy.) Only after a two year break from pre-ems were the grass roots able to grow.

    Here's an example of root pruning by pre-ems. The left plant is untreated crabgrass pulled in late June. Right plant is crabgrass, treated after germination, pulled at same time. Note the big difference in rooting. [​IMG]

    And look how roots are actually stubbed off. This is a blowup of plant on right above. [​IMG]
  9. Dman1214

    Dman1214 Banned
    Messages: 118

    There is such a heavy residual of pre-ems, it has been found that if you use the same pre-em product for 3 years on a lawn, you only need to apply at half rate after 3rd year for full efficacy.

    Jim - excellent post, right on the money. I am curious though about the above excerpt from your post. I don't think I have seen any research or data that supports that claim. Could you please post a link or point me in the direction to obtain that information? Thank you in advance. DMAN1214
  10. GroundKprs

    GroundKprs LawnSite Bronze Member
    Messages: 1,969

    Dman, I had experienced this myself about 10 years ago. Only had half the pre-em I needed so I cut rate in half and planned on using a lot of post emerg. Did not use any post spray.

    Last article I saw was 3-4 years ago in Turfgrass Trends, a supplement to Golfdom magazine. Was an article by a SC turfgrass researcher. I was surprised that this would be effective so far south. (Sorry I can't give a link. Golfdom TGT archives are only held online 2 years.)

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