Question for all you Herbicide Experts...

Discussion in 'Pesticide & Herbicide Application' started by csmlawn, Aug 15, 2008.

  1. csmlawn

    csmlawn LawnSite Member
    Messages: 106

    I've read here that the best time to apply herbicides for turf weeds is when the lawn needs cutting. Reason being is there is more weed present that can absorb the chemical. However, I asked my new lawn care contractor this question and he said right after a lawn has been cut. He feels that the blades are open and more vulnerable to the herbicide. He likes to hit the lawns no later then 3 days after a lawn has been cut.

    You're thoughts???
  2. RAlmaroad

    RAlmaroad LawnSite Silver Member
    from SC
    Messages: 2,257

    Most weeds die from trans-location. Inthat they transfer the toxins to the roots where they cut off the supply of food from the stem and foliage. Or, the toxin can preform a growth inducer and the weed dies prematurely. Other herbicides actually burn the plant leaf cells and the plants dies from the inability to take in carbon dioxide and preform photosynthesis.
    In any account, I prefer to have my clients mow three days before I apply any herbicide and not mow for at least 4 days after. Some labels even state it this way. I think Sedgehammer explains it in the label. A good clue is that the applications of a sticker means that the herbicide needs plant structure to attach itself.
    My opinion, I know but I have no problems or grips from clients with weed kills. However, I'm on those lawns every month or less to check the water and irrigation.
    You'll get conflicting opinions, I'm sure.
  3. bug-guy

    bug-guy LawnSite Bronze Member
    Messages: 1,032

    i agree the more leaf exposed the more herbicide gets on the weed, the better odds of success. it a perfect world grass geting cut 1x a wk 3 days before or after cutting
  4. junior091273

    junior091273 LawnSite Member
    Messages: 46

    I've had good results with Sedge Hammer with cut and uncut apps.

    Great Product.
  5. lilmarvin4064

    lilmarvin4064 LawnSite Senior Member
    Messages: 757

    ditto. The goal is to wait till right in the middle between mowings or at least a couple days after mowing. But you're much better off spraying right after you mow, rather than mowing right after you spray.

    when spraying nutsedge with sulfentrazone, I like to let it get tall.
  6. americanlawn

    americanlawn LawnSite Fanatic
    from midwest
    Messages: 5,955

    Best kill on weeds is when they are fully grown -- this way more AI (active ingredient) can be absorbed by the plant. Then wait 2 to 4 days before mowing or watering. Hard-to-kill weeds, wait 3 or 4 days. It is bad advice to mow off leaf tissue before spraying weeds. :hammerhead:

  7. rcreech

    rcreech Sponsor
    Male, from OHIO
    Messages: 6,163

    Weeds should be actively growing and healthy when applying herbicides.

    Now...if you are mowing HIGH, that makes a difference, but if you are scalping then I would say that your weed kill success will be limited!

    I would not ever recommend mowing before spraying.

    This is also why the label states to not mow 24 hours before or after an application!

    If it made the product work better do you think it would state that? :dizzy:
  8. kappa915

    kappa915 LawnSite Member
    Messages: 48

    I'm a 3 and 3 guy.

    Treat 3 days after mowing, don't mow for 3 days.
  9. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,800

    I am not sure mowing makes any difference. But I have heard it is best to spray at night. If the weed control drys on the leaf before it is absorbed--it is never absorbed at all. I would like to see some university research on this.

    On the other hand. Quicksilver (carfentrazone) and Dismiss (sulfentrazone) supposedly will not work in the absence of sunlight--also Octane. Do I have it right Shane?
  10. lilmarvin4064

    lilmarvin4064 LawnSite Senior Member
    Messages: 757

    you might be right on this. I know Scythe works much better in the sun, than in the shade.

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