crab grass cycle?

Discussion in 'Pesticide & Herbicide Application' started by rrbbtt, Apr 15, 2007.

  1. rrbbtt

    rrbbtt LawnSite Member
    Posts: 2

    I understand if I lay down a pre-emergent herbicide to control crab grass, it will stop the seed from germinating. Will the seed die or will it still be lying dormant waiting for the next opportunity to germinate?
     
  2. heritage

    heritage LawnSite Bronze Member
    Posts: 1,249

    The seeds that are ready to and do germinate will die as their root begins growing downward into the herbicide barrier.

    The seeds that are not quite ready to germinate will be unharmed by the herbicide, and often some of these seeds are ready to germinate after the herbicide has broken down later in the season, when the right conditions like rainfall and temps allow.

    Pete D.
     
  3. Puttinggreens

    Puttinggreens LawnSite Senior Member
    Posts: 369

    Do a search for Tupersan.
     
  4. turfsolutions

    turfsolutions LawnSite Senior Member
    Posts: 852

    I am always negative when it comes to Tupersan because it is a bit expensive, you need multiple applications, and I didn't see a big difference. Has anyone on this forum ever had good success with Tupersan? I dropped it from my arsenal a long time ago.
     
  5. Puttinggreens

    Puttinggreens LawnSite Senior Member
    Posts: 369

    I'm not crazy about tupersan either. But when faced with a spring seeding, which I try to avoid, it is still better than using nothing. What do you use?
     
  6. turfsolutions

    turfsolutions LawnSite Senior Member
    Posts: 852

    Nothing. I try and have all my spring seeding done by now and apply barricade (supposedly less harmful to roots) after a few mowings. I will spray Q4 on any crabgrass that does emerge. I do make sure that the customer understands that they can expect crabgrass issues that will need to be dealt with the first season. That they will need to aerate and seed again in Sept. By next spring the lawn will see the most noticable results with no crabgrass issues by then. Setting expectations in advance is critical to avoid controversy later. I have a letter template I use for each customer that asks for seeding in the spring to address this.
     
  7. xpnd

    xpnd LawnSite Senior Member
    Posts: 378

    Pre-emergents are best classified by their mode of action. There are the root inhibitors such as pendamethalin which allows the seed to germinate but does not allow a root system significant enough for success. There are photosynthetic inhibitors such as atrazine, simazine and dimension which allow the seed to germinate but when the product is absorbed does not allow the plant to manufacture food via photosynthesis. There are also root cutters but since I have never used one I don't know what they are.

    Pre emergents are applied for seed not yet germinated. Nothing really stops germination of seeds but it is the presence of the AI absorbed during germination by the seed, both desirable and undesirable, and the subsequent action of the AI on the seedling that makes pre-emergents effective.

    Down south here we have a much longer growing season than you guys do up north. Lesco has a neat crabgrass germination map that shows TX and 12 months germination. I do at least 3 pre-emergent apps each year. I would look at the possibility of doing split apps during the summer as we do. Yes it is more work but I think chasing crabgrass post is more work. I would look at Dimension. It is not only an effective pre-emergent but also provides reasonable post control on crabgrass not past the 3 leaf tillering stage. If your grass is on the label it might be worth a look into,
     
  8. rrbbtt

    rrbbtt LawnSite Member
    Posts: 2

    In my original post I was referring only to crabgrass seed. I only seed or over seed turf grass in the fall. Last year I had a flourish of late summer crabgrass and was trying to figure out where it came from. This year I am using Dimension because of its early post-emergence claim.
     
  9. xpnd

    xpnd LawnSite Senior Member
    Posts: 378

    Pre emergents are non selective. If you seed and apply a pre emergent too soon the seed will not take. If you seed to soon after an app, the same results.
     
  10. heritage

    heritage LawnSite Bronze Member
    Posts: 1,249

    Tupersan has a very short half life....Less than 30 days.

    So if you do some new seeding during, or right before crabgrass pressure, and decide to use Tupersan, be sure to get a longer acting pre-m down a month after the seeding w/tupersan. Use a pre-m that isn't so tough on the roots too.

    Pete D.
     

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