Herbicides in heat

Discussion in 'Pesticide & Herbicide Application' started by RigglePLC, Jul 14, 2018.

  1. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 15,022

    Seven herbicides were tested at 93 degrees for the chance of burn or injury to cool season grass (rye and bluegrass). Herbicides were: Drive, Quicksilver, three-way, three-way plus surfactant, Speedzone, Surge, and T-Zone.
    The methods could not be precise. The squirt sprayers applied about one milliliter per squirt applied to a seven inch circle. This was about 1 gallon per thousand sqft.
    Then I applied 3 times over for comparison. Then 5 times over for comparison in a grid pattern.
    Of course, this also increased the amount of water carrier applied.

    There was no injury, after 8 days.

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    That Guy Gary likes this.
  2. That Guy Gary

    That Guy Gary LawnSite Silver Member
    Messages: 2,041

    I think good irrigation makes a difference.

    I've spot sprayed in low 90s from my Exmark when mixed for 4k per without any burn but I won't squirt if it's dry.
     
  3. roody2333

    roody2333 LawnSite Senior Member
    Messages: 990

    isn't 90 around the max labels suggest? 93 is not that far off, but besides that I think the major reason why there was no damage (at least so far) is because that grass wasn't already dormant brown in which case it might never bounce back out of dormancy if sprayed.
     
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  4. That Guy Gary

    That Guy Gary LawnSite Silver Member
    Messages: 2,041

    Yeah, most say no broadcast over 90 and be willing to tolerate injury if you spot spray.

    Some of the specialty chems aren't as restricted, quin (Drive XLR8) and I think Sedgehammer don't have that on the label.

    If I ever have my ride on home on a hot day I might broadcast a few hundred sq ft and see what happens. I think turf health is the key though just like you said, well fed and watered grass can tolerate more chems in the heat than stressed or dormant turf.
     
  5. lawn king

    lawn king LawnSite Silver Member
    Messages: 2,543

    I pull the plug altogether on weed spraying at 86-89 degrees. I think the safest heat herbicide is quinclorac wettable powder. I do think mso as a wetting agent greatly improves the performance of quinclorac, but you really have to be careful in the heat with mso! I did some test spraying in my own yard and there would have been turf injury had I not nursed the areas with water. A little mso goes a long way.
     
  6. walkinonwater27

    walkinonwater27 LawnSite Senior Member
    from ct
    Messages: 316

    They do not recommend not spraying above 90 because you will hurt the grass, it is because the chemicals volitize and turn into a gas. When spraying around 90 your very likely to damage plants near where you spray even if your not close to them. I have seen it happen on tomatoes, your best bet is to spot low to the ground with Handcan. I do not spray off the rideon over 90.
     
  7. walkinonwater27

    walkinonwater27 LawnSite Senior Member
    from ct
    Messages: 316

    If it’s really hot 100 plus , the sprays evaporate so fast the weeds show little to no injury .
     
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  8. That Guy Gary

    That Guy Gary LawnSite Silver Member
    Messages: 2,041

    Tomatoes are insanely sensitive, mine start to wilt if I say "Roundup" close enough for them to hear me.

    The labels clearly say not to spray above 90 because it may injure the grass, are they lying about that?

    Every product label I've read (I don't spray esters, but I think I should) that is labeled for weed control in planters, hardscapes, other places besides a lawn basically mentions nothing about temperature unless I'm spraying turf.

    Amines are salts. Salts can dehydrate things through osmosis. Pull what little water is left out of drought stressed turf and you get dead or severely injured turf.
     
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  9. walkinonwater27

    walkinonwater27 LawnSite Senior Member
    from ct
    Messages: 316

    I had some college professor tell me that at a class for license credits but your thoughts make great sense as well.
     
    That Guy Gary likes this.
  10. walkinonwater27

    walkinonwater27 LawnSite Senior Member
    from ct
    Messages: 316

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