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Killing weeds in the moon light.. well.. almost

Discussion in 'Pesticide & Herbicide Application' started by Rayholio, Aug 3, 2007.

  1. Rayholio

    Rayholio LawnSite Bronze Member
    Messages: 1,461

    So, I have a couple lawns that are in desperate need of weed treatments.. I'm thinking of doing the work after 7pm.. just when the temps are below 85... maybe more like 8pm

    I'll be using Q4 on fescue. does anyone know how long the temps need to be in the safe zone (85 or less) after the treatment to avoid turf damage?

    Perhaps I could do the treatment in the morning instead, if it only has to be below 85 during the treatment,,, or maybe the treatment can't be done at all until fall..

    Perhaps someone could explain to me exactly what happens to the chemicals that kills the grass in high temperatures?
  2. mkroher

    mkroher LawnSite Senior Member
    Messages: 539

    wait until the fall. that's the better time to control broadleaf anyways.
  3. Ric

    Ric LawnSite Fanatic
    Messages: 11,969


    Many Chemicals are Heat reactive. Therefore The next Day when the Temperature jumps back up to 95 degrees, your night time spray job is the same as if you did it at High Noon.

    I am not saying you can't do Weed Control in the middle of summer. Just cut your rate in Half try a sample spot or two.
  4. Rayholio

    Rayholio LawnSite Bronze Member
    Messages: 1,461

    Someone once told me (don't ask me who) that a porton of the spray will vaporize during the spray job due to high temps, and that those vapors are what's dangerous, as they would hang low, and effectively fog the turf.. where as the properties of the chemicals change in vapor form, it can kill like round-up... meaning that if you could do a treatment in temps where evaperation was not possible, then you would be fine....

    So what you're saying is that it's something that happens inside the plant, and not a product of evaporation / vaporizing chem..

    Which is fine... We will still get a cool day every now and then.. the labeling doesn't tell me.. so how many hours do I need before re-heat? 12-24-36??
  5. Ric

    Ric LawnSite Fanatic
    Messages: 11,969


    Ester Herbicide will vaporize after application and drift off the target application and can kill many non target plants in the higher temperatures of summer. Esters are what we call hot herbicides because they work so well and can easily kill the desired turf we are trying to manage. In cool weather they work better than amine herbicide. Ester Herbicides should not be used in temperatures over 80 degrees.
  6. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,562

    We don't worry about herbicide damage to grass or drift up to about 90 degrees--using high volumes of water--about 3 gal per thousand sqft.

    May I suggest Surge herbicide? On the label it says "Suitable for applications up to 90 F".

    I have heard our weed professor say that nighttime, high humidity, and rapid weed growth (young weeds) are ideal for weed control.
    He explained that: at high temperatures, and low humidity the herbicide dries and crystalizes on the leaf surface. Once it crystalizes it can no longer penetrate the weed--that percent of the herbicide that forms crystals --is wasted. Esters don't crystalize as much as amines--if i understood him right.
  7. rcreech

    rcreech Sponsor
    Male, from OHIO
    Messages: 6,153

    Typically the best time is to spray in the morning or in the evening. This is when the plants are the most active, as they have a tendency to "shut down" during the afternoon to conserve energy and moisture loss.

    Several years ago there was a research trial using Velvetleaf (which is one of the harder weeds to kill due to its very hairy leaf surface). They showed that between 11 am and 6 pm there would be considerably less kill. Anytime before 11 or after 6 it worked much better. Now this was a glyphosate trial on velvetleaf....but this tells us how weeds are affected during the day and how the temp can affect herb intake.

    As Riggle says, I think you should be fine spraying later in the evening. I have even sprayed about 85 deg with 3-Way and I have never had any product walk away from me yet. Dicamba can be just as bad or worse as far as volatilizing. Two things that affect it most is humidity and wind!
  8. DSTC

    DSTC LawnSite Member
    Messages: 130

    What kind of turf and what type of weeds?

    I pretty much can't use anything with Dicamba and 2-4-D after April (sometimes March) in my area. We have very high temps and humidity here, so esters and the like are pretty much out for summer weed control. I have had a lot of luck with a product called Manor. I do believe that there are generics, but we just always call it manor. The A.I. in this one is Metsulfuron.

    Check the label on this one though because it can pimp slap Bahia grass. I think it is labeled safe for Fine Fescue and KY Bluegrass though, but definitely check if you look into this one. We only have Centipede, Bermuda and St. Augustine around here, and centipede is a little bit sensitive to this herbicide at higher rates.
  9. Rayholio

    Rayholio LawnSite Bronze Member
    Messages: 1,461

    Well.. I was planning a Q4 app on fescue.. it would be probably right at 85 degrees.. but quickly falling, humidity will be fairly high. the sun would be low in the sky.. so direct sunlight would be minimal. The guy has some clover.. plenty of crab grass, and other junk weeds. someone skipped his pre-emergant this year, and it's been outta control.

    so it sounds like I'm going to be pretty safe with the Q4 in the evening, as the main concern is vaporization...

    Hey, Thanks for all your help guys.. this board has saved me a lot of pain.. gotta lot of respect for you fellas that had to learn the hard way!!
  10. boats47

    boats47 LawnSite Member
    Messages: 244

    Ray I had to spray this property last week and the temp that day (and the rest of the week) hit 92 and has stayed pretty consistant all week. Thier lawn is fine, well execept for the weeds...Yah they got smoked. I did use Q4 on that property and used it on my lawn to monitor the effects with temps so high this week. Other then the crab grass and other weedy friends looking like they were hit with Napalm, there is no damage to the turf. This Q4 has got me sold, so far.

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