Hot temperatures and herbicide

Discussion in 'Pesticide & Herbicide Application' started by RigglePLC, Aug 1, 2011.

  1. RigglePLC

    RigglePLC LawnSite Fanatic
    Posts: 12,111

    I have heard several people comment that they do not spray weed at high temperatures for fear of turf damage and fear that the weeds would not be killed. Our neighbors to the south seem to think 90 degrees is fine. Therefore...
    I decided to test the theory on my vacant lot--I mean at the Micro Turfgrass Research Center. But then it got slight cooler so it was only a humid 93 degrees temperature at the time of the test and it has been about 90 to 92 as a high in the last few days. 33 degrees Celsius. Heavy rain a few days ago--soil was moist. Rye, blue and fine fescue.
    I sprayed a circle 13.5 inches in diameter, (equals one square foot). I sprayed spots for one second, 3 seconds and 5 seconds. Simulating about 1 times label rate, 3 times, and 5 times label rate. One second is about a third of an ounce of spray solution.

    I sprayed:
    Lesco Eliminate
    Gordon's T-Zone
    BASF Drive

    Thus far at 36 hours, no injury to the grass. Slight effects on the few weeds in the spots.

    I also treated poison ivy, and a few spots of weedy trees and brush nearby with Drive. Killed a few inches of a wild grapevine. Injured a bit of black locust. No visible effect on poison ivy, nor mulberry, nor box elder.

    Stay tuned.
     
  2. Laner

    Laner LawnSite Senior Member
    Posts: 325

    I can confirm slight turf damage from applying Trimec 992 at 82 degrees at time of app with full sun and no rain for 6 days. This was checked 5 days after app. Grass displayed yellowing. Should come back fine with rain but still raised concern.
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  3. lawn king

    lawn king LawnSite Silver Member
    Posts: 2,274

    This time of year (for the most part) we go to a full rate quinclorac, 1/3 rate eliminate, & wetting agent. Its very hot here in july & august & this combo is very stable in the hotter temps. This combo is good for a strong knockdown on clover, spurge, and crabgrass. When things cool down after labor day we will change up our formulation.
     
  4. grassman177

    grassman177 LawnSite Fanatic
    Posts: 9,795

    waiting fo the temps to drop here. 102-106 today and just as or hotter tomorrow. not too shabby huh
     
  5. DA Quality Lawn & YS

    DA Quality Lawn & YS LawnSite Fanatic
    Posts: 8,872

    Full sun does seem to have an effect on apps in hot weather, no?
     
  6. Smallaxe

    Smallaxe LawnSite Fanatic
    Posts: 10,080

    Drought plus heat on sandy soil, full sun... MN, WI, and MI really haven't had drought during July... Just oppressive heat and humidity, from the midwestern POV anyways...
    How's IL anyway...? :)
     
  7. vencops

    vencops LawnSite Bronze Member
    from NC
    Posts: 1,537

    Question:

    We have cool season grasses, for the most part, here. Since my spray career is in its' infancy, I admit to being gun-shy on risking turf damage, this time of year.

    But, I also have to think.....

    Let's say I'm successful in killing out the undesirables in my customer's lawns.

    What now? Over-seed?

    I could be completely naive...or, just plain ignorant. But, I'm not going to kill anything, until I can replace it with something better. And, I'm not thinking August in NC is the time to sew grass.
     
  8. RigglePLC

    RigglePLC LawnSite Fanatic
    Posts: 12,111

    I have never had to seed where the weeds were killed. Its gradual and the grass fills-in--usually. Anyway the customers will call if there are weeds in the grass.
    I hate spurge.
     
  9. vencops

    vencops LawnSite Bronze Member
    from NC
    Posts: 1,537

    Crabgrass - I agree. I'm tempted to spot-spray these, now, also.

    Bermuda grass? It's a PITA, here. If I killed out bermuda patches, now.....I'd have bare spots. I'm seriously wondering if total control of this scourge is possible (here).

    I don't really have any other weeds to speak of in my high-end (the ones where I spray) lawns. I'm not saying there's NO other weeds. There's just not anything to get upset over.
     
  10. cgaengineer

    cgaengineer LawnSite Fanatic
    Posts: 15,782

    Your southern friends have dead fescue at this time of the season anyway...if its not dead its damn near it! Anything alive right now is bermuda and you can just about spray it with RU and not kill it...it may stunt it, but it likely will come back.

    That being said, I do not use 3 way on bermuda in the heat, but I'll spray celcius all day long in the 90's...even on some non-irrigated lawns. Depends on the lawns health.
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