Can someone define root pruning?

Discussion in 'Pesticide & Herbicide Application' started by CT John, Oct 13, 2005.

  1. CT John

    CT John LawnSite Member
    Posts: 90

    There is only limited reference availible doing a web search. I'd like to understand how pre-emergents root prune and which ones are worse than others. Thanks.
     
  2. MIDWEST25

    MIDWEST25 LawnSite Member
    Posts: 97

    they all damage root systems.dimension probably the least.applied in combination with fertilizer will increase thatch in turfs with rhyzomes such as bluegrass which already has a weak fiberous root system to begin with and shallows on its own during hot dry weather.my best looking lawns never get pre-emergents of any kind.the mowed low no water lawns always get pre-emergents and crabgrass.you figure this out from here
     
  3. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    DNA herbicides such as Dimension perform what you refer to as root pruning. There was a study published on the web (cannot locate it) comparing the root damage of several commonly used herbicides. The study showed that Dimension and Pendimethalin were two of the highest in potential root damage. Barricade was less harsh on the root systems, while Ronstar had virtually no effect. This is because of differences in the mode of action (MOA).

    The information I'm referring to showed photos of turfgrass roots that were subject to the various herbicides. You could see the difference from the photos, and how the root systems were "clubbed". I didn't bookmark it, but wish I had now.

    Here is a link that discusses root pruning.

    http://www.btny.purdue.edu/weedscience/moa/Root_Mitotic_Inhibitors/text.html
     
  4. Ric

    Ric LawnSite Fanatic
    Posts: 11,957

    Turf

    Great post and The Debate of Chemical root pruning has been hashed over many time in many universities. There are two schools of thought on pre-emerge. Those who feel it's benefit out weight it disadvantage. And those who think it's disadvantage out weight the benefits. Ronstar the last time I checked was not labeled for Commercial or Home lawns. I don't believe in Pre emerge on most Turf Grasses my self and prefer to spot treat post emerge which as Turfunlimited has point out, has stunting effect on the desired turf plants as well, even as a selective. I personally feel a strong root system will with stand all kinds of stress better than a poor root system. There are PhDs who will disagree with me and PhDs who will agree with me about Pre emerge.
     
  5. CT John

    CT John LawnSite Member
    Posts: 90

    Great replies and thanks for the link Turf.

    Is there a school of thought on how long an affected plant takes to recover? I would assume it begins happening as soon as the chemical degrades enough in the soil. Does it affect mature plants as well as newer seedlings? I'm sure the stress is much more prevalent in the younger plants.
     
  6. Ric

    Ric LawnSite Fanatic
    Posts: 11,957

    John

    Like any chemical, the soil has a lot to do with the residual effect. Clay soils will hold it longer than Sandy soils. But, yes there is a long term residual that many who believe in Pre Emerge take advantage of by decreasing rates in next years application. Those of us on the other side of theory find this residual as a disadvantage. I am not going to try and convince you which theory is best. Pre emerge works by stunting the singular root which first emerges from a fresh germinated seed. With out a food source that seed dies. In a mature growing plant new roots also put out singular hair roots that are effected in the same way. Hence the term Chemical root pruning. Here in lies the whole debate about pre-emerge and it's value. I did not read the link, therefore I may be either repeating information there or contradicting it.
     
  7. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    Obviously, herbicide damage would be a more serious problem with new seedlings. Established turf can recover from clubbed root problems much better than new turf with immature root systems. This is why most pre-emergent labels suggest only using on established turf.

    When dealing with warm season turf, this is less of a concern because seeding is not part of the normal management practice.

    However with cool season grasses such as Fescue, I normally apply pre-emergents as little as possible. For at least 4 months per year, there is new seed either germinating or becoming established.

    And anyone dealing with athletic fields should be using Ronstar by default. Ronstar has a different MOA which does not cause root damage. Your fields are already stressed from the traffic, so this doesn't compound the problem.
     
  8. Ric

    Ric LawnSite Fanatic
    Posts: 11,957

    Turf

    Theory Vs Theory. But I feel on the solmatic warm season turf, Pre-emerge has greater disadvantage than advantages. As Solomatic turf grow on top of the ground where the true Barrier of Pre-emerge is or should be.

    Ronstar also has its disadvantages because of its MOA. It does not stop all regrowth as good as a DNA pre-emerge. I have only had little experience with Ronstar and that was only a small amount of involvement with a 419 Bermuda sprig job for a New Golf Course. We experienced some regrowth, but not what I would call uncontrollable by any means. I think is wasn't any more than expected. This was on Fairways of native top soils fresh dug and brought in.
     
  9. CT John

    CT John LawnSite Member
    Posts: 90

    Thanks again for the posts guys.

    Ric, now your speaking of a longer term residual than the general, say, 3 or so months of control that is commonly accepted? Yeah, I would say thats a disadvantage. Then why use subsequent applications? It obviously can't be the same level of control past the 3 month(generally) point, is it? Understanding the many variables involved.
     
  10. Ric

    Ric LawnSite Fanatic
    Posts: 11,957

    John

    Cut to the bottom line. A thick well managed healthy turf is its own Weed Control. You get that Healthy turf with Roots. I was trying to keep my own bias opinion of pre-emerge herbicide in perspective. But I am sorry I am of the school where pre-emerge is only used in rare cases for control. Therefore I don't study the residual of them and if I did my results would vary from your because of soil types.
     

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