dishsoap on plants as 'pesticide'?

Discussion in 'Organic Gardening' started by candychikita, Apr 15, 2009.

  1. candychikita

    candychikita Member

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    langley, bc canada
    hello all!

    so my dad, the genius, sprays his apple trees with dish soap if he sees pests on them. (dish soap like the palmolive stuff sitting underneath our sink) he goes out every day and picks off diseased leaves/one with bug bites on them, and then sprays liberally a mix of 50% dish soap/50% water on the leaves, especially the undersides. he has never had any severe pest problems, and now he's doing it to his cherry trees as well...he swears by it.

    i say 'the genius' because he knows so much bizarre old fashioned stuff that works! so...has he just been lucky, or is dishsoap an effective and organic 'pesticide'? comments?
  2. joclyn

    joclyn Rising Contributor

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    philly, pa, usa 6b
    yes, liquid dish soap can be used as a pesticide. i wouldn't use such a strong solution, though. usually a few drops in a gallon is all that's needed. you can also put in a few drops of cooking oil, too.

    pretty much, that's what the stuff on the store shelves is made of...just costs a lot more than making it up yourself!
  3. greengarden bev

    greengarden bev Active Member

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    SW Ontario, Canada
    I'd add that if you don't want to buy specialty insecticidal soap (such as Safers) you should use plain old-fashioned dish soap-- no "antibacterial" additives.

    Commercial (Safers) soap is not quite the same thing as dish soap. The commercial stuff is designed to be used as a pesticide, using unsaturated long-chain fatty acids. The recommended rate is 1 tsp per litre (1: 200 or 2% solution) which is the rate most often recommended for dish soap as well.

    There are a variety of opinions on the use of dishwashing soap as a pesticide. Iowa State has a "pro dish soap" article:

    On the other hand, the University of Illinois comes out against it, and recommends using commercial soaps such as Safers:

    Whichever experts you believe, it is important to remember that the spray has to actually HIT the bug to have any effect. And it generally works on soft-bodied insects (aphids, caterpillars, mealy bugs, mites, soft scale, thrips and whitefly) , not hard-bodied insects such as beetles.

    I did some research a while ago and learned that olive oil contains a high percentage of the unsaturated long-chain fatty acids that make an effective pesticide. The soap that is made from olive oil is called "Castile Soap" and you can buy it from soap crafters. I think I paid $10 for a 1/2 lb chunk of it, which made it quite a bit less expensive than the Safers liquid. One drawback, though, is the work involved in grating the soap so it'll dissolve in water. As well, you just need to guess at the amount to use -- the usual ratios don't apply on non-liquids. I still have some of that Castile Soap around somewhere, but it was so inconvenient that I just use Safers now.
  4. Millet

    Millet Well-Known Member 10 Years

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    Denver,Colorado USA
    AZ41 is a newer organic insecticide-fungicide-nutrient that I have just recently used on various greenhouse crops. So, far I have only used it on aphids and white flies. The control of aphids was 100 percent, and the verdict is still out on white flies, as I have only sprayed them once. The big four greenhouse insects are aphids, white fly, scale and mealy bug. AZ41's label claims control of all the above insects, I hope so, so far I have only sprayed for the two I mentioned above. - Millet (1,375-)
  5. Yubalover

    Yubalover Member

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    Sierra Nevada Foothills
    I've used L.O.C. (an Amway brand) for over 25 years on my roses to prevent aphids. On years where I have been avidly gardening I apply 1/4 tsp. at the base of each rose plant and soak it into the soil with some water. The plant takes it up through the roots and keeps the aphids off the blossoms. However, I also make a spray solution and periodically spray new growth. Usually 2 tsp. per quart of water. It works!


    Good luck!
  6. eldumas

    eldumas Member

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    Maple Ridge, BC, Canada
    I use a mix that was recommended by Jerry Baker, a rather well known gardener in the US. His formula goes something like this. Use a 20 gallon hose-end sprayer, which means that a bottle attaches to the end of your garden hose, and the bottle drains in 20 gallons of water from the hose.

    In the bottle put in about 1/2 cup of liquid dish soap. I use a lemon scented soap which pests do not like, and I specifically avoid the anti-bacterial things because of the problems of creating resistant bacteria.

    He also suggest putting in the bottle some liquid lawn food, but I use Miracle Grow because it is water soluable (that is important). You can also change it up once in a while to a fish fertilizer, but it will smell a bit. Whatever food you use, do it at about 20% of the recommended dose, because the soap is a surfactant, which means it breaks down surface tension and the plants take up the food better. This also stretches your fertilizer budget! I put in the bottle about 1 cup of Miracle Grow.

    Then add about 1 cup of ammonia (yes, good old fashioned ammonia that you can buy at London Drugs for cheap). Ammonia is just another form of nitrogen, which all plants need. By adding ammonia, you are "seeding" the nitrogen cycle in your soil, which helps plants take up food and water better.

    Fill up the bottle with water, drop in a golf ball to stir it up, and spray it over everything in your yard. As you water the plants, you are also feeding them and getting rid of pets.

    If you really want to go nuts, add about 1/2 cup of freeze-dried tea to the mixture. This is an excellent gentle food that all plants just love, and they will reward you for it with huge growth. BUT, I have been able to only find the powdered tea in the US. You do not want our Canadian ice tea mixes that are all about sugar. You just want the tea. AND, be careful what you overspray with the tea, as it leaves a brown residue on pots and decks. It comes off, but gives you more work to do.


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