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Dishwashing detergent as a surfactant

July 18, 2007

I've seen, on this forum, to use anywhere from "a few drops" to a teaspoon of dishwashing detergent per gallon of whatever to act as a surfactant. That's a pretty wide range, IMO. Can someone/anyone narrow it down a bit ;-)



Comments (18)

  • krazyjorge0424

    I agree a few drops is a wide range but whatever the amount is be careful not to burn your roses because I already did that with soap LOL!!

  • rose_nutty

    I believe that you don't want to use certain brands (Dawn, for instance). I've used Palmolive for years with no problems. I use approximately 1/8 teaspoon in a 2 gallon sprayer. I use it for not only fungicides but also broadleaf weedkiller (2,4-D) and Roundup to improve their effectiveness as well.

  • banders

    Thanks, I'm also wanting to use it with Manage (SedgeHammer) for nutsedge.


  • michaelg

    Are we talking about sink detergent or dishwasher detergent?

    I use 1 Tsp of Ivory Liquid per gallon, but if you have hard water, more would be needed. I use 4 Tsp / gallon as an insecticide with no damage so far. It doesn''t get real hot here.

  • roseman

    Here's my "narrow down," don't use it at all. You have to be very careful when using dishwashing detergent for that purpose, because there is always the possibility of burning the foliage. There are surficants available in the market place that have specific directions and will not burn the foliage. They are the ones I have always used, and a good one is Indicate 5, which can be had from Rosemania, see link below.

    Here is a link that might be useful: Rosemania

  • banders

    michaelg, I'm talking about dishwashing detergent--Joy is what I have on hand. "A few drops" per gallon didn't seem like enough to me, 1 tsp would probably work--my water is city water and not particularly hard.

    roseman, I'm going to be using it on a mostly dormant fescue lawn. I don't think I can hurt it ;-) And I *do* want to hurt the nutsedge.


  • michaelg

    When my rose mentor decades ago had a nutgrass problem, she finally went on a rampage, moved the ornamentals into pots, sprayed a quarter of her garden with Paraquat, and covered the area with black plastic for three months. When she took the plastic off and started replanting, the nutgrass grew back fine as could be.

  • banders

    Right. Manage, newly named SedgeHammer is one of two things that will kill it--the other is Image, but I've read better result on Manage. It may take several years to get rid of it, but it works. I'm gaining ground, so to speak. I've never used a surfactant, so I thought I'd try one this year--to improve my odds.


  • dublinbay z6 (KS)

    Why not use Dawn dishwashing soap as a surfactant? What other dishwashing soaps should be avoided?


  • mike_rivers

    It's a simple matter to determine how much detergent is needed. Just make up your spray solution and add measured 1/8 tsp increments of detergent until you see a smooth film on the leaf's surface. In my garden, with Infuse, I see only a few beads of water and very little film formation with no detergent. With 1/8 teaspoon Joy per gallon, I see at least 90% coverage and no beading and with 1/4 tsp per gallon, I get essentially 99% coverage.

    Liquid dish detergents, including Joy, are sometimes sprayed as insecticides, usually at 1 to 2% concentration (2 1/2 to 5 tablespoons per gallon). I have never seen spray burn with 1% concentrations and I think it would be very unlikely to see any spray burn at all with 1/4 teaspoon per gallon with any liquid dish detergent on the market - I admit that Michigan temperatures are not exactly the highest in the country.

    Most surface fungicides, such as Daconil and Manzate, have very low water solubility and are usually sprayed as emulsions. The emulsifying agent is also a surfactant and no additional spreader should be necessary. Bayer's tebuconazole spray also fits in this category but most systemic fungicides have sufficient water solubility to be sprayed as true solutions - that's why they are absorbed into the leaf in the first place. Immunox, Funginex and Infuse fall into this category and each of these will probably benefit from addition of a surfactant.

    One more point: Manzate sprays should not require addition of a spreader, but Manzate is unstable at high pH values and lowering the pH, perhaps with Indicate 5, is usually beneficial.

  • michaelg

    Liquid products usually have a surfactant added, so you are just making an adjustment for the quality of your water and the shininess of the target foliage. No adjustment is needed if the solution sheets on fully expanded leaves. (I don't try to make it cover the emerging leaves, which are very waxy. Not sure whether that is a correct policy or not.)

  • banders

    I'm only going to be using 1 gallon of solution, total, so there's no room to experiment. Since I'm not worried about foliage burn, I'll use 1 teaspoon of Joy. Nut sedge, look out! ;-)


  • rockyflorida

    this is a little off topic, but I have noticed that if I spray very early when the foliage is slightly moist from dew, the coverage is much better and the leaves are more evenly wetted even though I use Indicate 5 all the time. It seems somehow that the condensation manages to stay on the leaf and keeps what you spray on better. This is a completely unscientific observation!

  • hummersteve

    Possibly some of you are missing the point, The idea for some of us is to spray for plant uptake and that should be done early morning when the stomata pores are open otherwise youre wasting your time. If you are spraying for insects thats a different story.

    I used to use some coco wet which Im out of now, but the instructions for it was to use 1/4 tsp per gal.

  • fragrancenutter

    I use the cheap stuff from Coles at $1 per litre! Never burnt anything with it!

  • Buford_NE_GA_7A

    Thanks hummersteve, I didn't know that.

  • seil zone 6b MI

    I use the Spray n Grow Coco Wet too and I like that very much. I don't think I would try soap. I tried a home brew spray once that had cooking oil for a spreader/sticker and I had Kentucky Fried leaves in not time, lol!

  • skweiss46

    I just want to use household vinegar so that it is not toxic to pets, bees, etc. I want to kill/burn unwanted grass and weeds in borders, between paving stones for instance. I always put at least a tsp per gal of dish detergent in it so that it will stick. I am going to try 1 tableson per gallon since I WANT it to kill burn stuff. It seems to Sometimes work but of course I have to keep doing it. But at least i am not using longlasting poisons or Roundup which i understand is not always so benign. Is there anything wrong with this, does anyone think?

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