Water affecting herbicide efficacy

Discussion in 'Pesticide & Herbicide Application' started by Landgreen, Mar 3, 2013.

  1. Landgreen

    Landgreen LawnSite Senior Member
    Messages: 252

    Last year was difficult for me to control weeds. I have never had such poor results. Years past have not been an issue so I am trying to cover every factor of why such poor control. I am applying low odor triplet out of my z-spray. 1.5 oz per M. Now last summer was THE hottest on record for my town here in Nothern Michigan. Obviously I had to skip certain days and wait for cooler temps. I think another issue was I let the spray mix sit in the tank for a few days on a couple occasions. So one of the factors I wanted to eliminate was the water I am using. It's my understanding that a high pH combined with high amounts of Ca, Mg, and Na, (hard water) will affect the efficacy of the herbicide. So I had the well tested where I mix. I had these results:

    pH- 6.8

    Concentration of:
    Ca- 2.0 PPM
    Mg- 1.6 PPM
    Na- 165 PPM

    I was wondering if anyone else has had their water tested and how it compares. I'm not sure who would be a good consultant on this matter. I've only gleaned what I know from some articles written about it by a few universities. Any help would be appreciated. Thank you.
  2. windflower

    windflower LawnSite Bronze Member
    Messages: 1,098

    Hot dry conditions will affect how well the herbicides are absorbed. It also may favor weed growth rather than the turf. The water quality does make a visible difference. I try to use city water rather than well water if possible. Haven't tested any wells but biggest offenders here are iron and calcium in the water. I think you can get water conditioning tablets to add to your spray mix.
  3. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,675

    What weeds did you have trouble with? Crabgrass? Spurge? Oxalis? Purslane? Black medic? Poison ivy?
    What dates did you apply the herbicide? How many ounces Triplet did you add per tank? Did you use surfactant? About what gallons (or ounces) per thousand sq ft did you apply?
  4. Landgreen

    Landgreen LawnSite Senior Member
    Messages: 252

    Spray mix out of my z-spray is 1/3 gal/M.
  5. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,675

    Sounds like a good mix to me. And the water looks excellent in my opinion. Dry conditions at fault perhaps.
    Did you try it a few times to be sure you were covering 3000 sqft per gallon?
    In most of the country 85 is not considered hot--they keep spraying. LOL!
  6. CalGlaspie

    CalGlaspie LawnSite Member
    Messages: 2

    There is never ever one reason as to why weeds might not have died but always ways to improve weed control.
    Although temperatures might not have been in range to injury your turf, most herbicides act on actively growing weeds. If temperatures are in excess and moisture is limited, growth can but slowed and herbicides can be rendered ineffective (think about spraying when its 40 outside and how good of control you get).

    Tank water "hardness" (soluable salts) generally only affects certain chemicals (roundup to name one). I would worry more about letting it sit in the tank depending on the chemical in question, herbicides can fall out of solution or degrade in the spray tank effectively cutting your rate. For instance, some of the SU (sulfonylurea) herbicides can degrade to nothing in a few days in a spray tank (depending on pH of course). Again, this depends on the chemical and most of the three way herbicides are a little bit more resilient.

    Your application method could also be to blame as well, make sure to calibrate nozzles on your zsprayer and check pattern as tips can wear out and cause a poor spray pattern and poor control. An easy way to check after the fact is to see if there is a pattern of poor weed control (strips of weeds).
    You may be able to increase control by adding ammonium sulfate or another nitrogen source to cause weeds to grow.

    Lastly, if this is something you are noticing year to year
    1) You are going off relative memory and weeds really aren't any worse (we are all guilty of doing this). Unless you are actually keeping decent records of weed control ratings I would caution against trying to recall year to year weed control.
    2) Weather is always different year to year and warm years all around are bad for turf and bad for weed control.
    3) Something internally changed. Be it how you mix chemical, who sprays it, or how it was stored it really doesn't take much to go from 95% control to 70% (we had a tech who decided one season to not overlap spray patterns and we had strips of crabgrass where the outer fan of the pattern was minimal).

    Good luck this season knocking um dead!

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