Treating tomato plants with dishwashing soap

susanbf714May 10, 2011

This is my first time here, so i hope i am following the rules. I've grown tomatoes all my life (it really is a "Southern" thing), and so did my mother, my grandmother, and my great-grandmother, so i'm here to share a few "tips." Yes, i do spray my vegetable garden, especially tomatoes, with dish soap, using only a few drops, and lots of water. It has worked for our family for well over 150 years. The insects don't like the soap, and neither does the tomato horn worms (scary, but cute). To keep other "critters" out we "scatter" hot sauce, pickle juice, and cayenne pepper generously over the soil area, and sometimes we mix the pepper with some water in a spray bottle, and spray a few each and every time. The hot sauce and pepper spray will not hurt the plants, nor will the dish soap. I do; however, at least once during my garden season, use Sevin just works good, and you are going to wash off your vegetables. Another good tip, and this is a good one, because most people just don't think about it....i hate spiders with a passion, but i know what a garden spider looks's big and yellow and weaves the most incredible webs you will ever also "eats" most pests and insects in your garden, so DON'T kill them. I know it's a natural instinct to kill spiders, but try really hard to not kill the garden spiders, they are nature's best defense against the "pests" of your garden, any garden as far as that goes. Plus you will witness the amazing creativity of these webs....truly God given. My secret for big healthy tomatoes...soil and good drainage. I have three (3) compost piles where we place grass and pine cone mulch, leaves, sticks, and coffee grinds. When it's time to plant (and i always do before Good Friday because my great-grandmother told me to), my husband and i rake back the top layers, and we find the blackest dirt full of earthworms waiting for us. You know it's good soil if earthworms are crawling in it. Rake away the worms, but don't kill 'em. Shovel some of that black dirt in a separate pile. Make sure your worms go back in the dirt. Rake the top layer of mulch and cuttings back on top so that the compost process will continue. Now you have a good size pile of rich, fertile dirt. Mix with 1/3 part of garden soil, and 1/3 part of manure, and a little of peat or potting soil. Mix WELL. If you are using a ground level garden (you use a tiller to break up the ground), throw that dirt on top and between your rows...then do your planting. Since we are older, and arthritis sets in, we now only do "raised-bed" vegetables garden, so we fill up our containers with the good soil and plant. We have always had the best vegetables using this combination of soil. Oh, i forgot, there is something you should try to also help keep pests grandmother and grandfather always planted sunflowers, zinnas, and marigolds in the gardens....they said the "smell" keeps the tomato horn worms away, and basil, the smell of basil is offensive to some insects too. But again, if you want to keep the squirrels away, and other critters, put that hot sauce and cayenne pepper out, and the dish soap. It works every time for us! We also keep adding fresh compost dirt to the gardens a couple of weeks, and garden fertilizer. We even use kiddie pools to raise squash, cucumbers, and zucchini. Just drill holes for drainage. And i always put broken tiles and rocks for extra drainage. Like i said, it works for us, and the soap is not going to hurt any animal or birds. We place cayenne pepper in our bird feeders to keep the squirrels away, works every time. And that is the end of this post, hope i did ok.

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rhizo_1 (North AL) zone 7

You did just fine, Susan. It's always great to hear from gardeners with generations of experience behind them. I agree that those big garden spiders are amazing. I used to fear them horribly as a child, though. They would string their webs between the corn stalks in our big family garden, and I'd have to run and hide before supper time so that I didn't have to go out there and pick corn! (I've pretty much mastered my fear, though.)

Truly, the only negative comment I would make would be in reference to your use of Sevin. I know that it has been around forever, but it is surely one of the worst chemicals when it comes to harming beneficial insects and other critters. Sevin is absolutely lethal to earthworms. Maybe, if you visit some of the other forums, you'll find an alternative that is worth trying.

I see that you are from Alabama. I hope that you live in an area that wasn't hit by one of the many tornadoes that ripped through our state. Those of us in Northern Alabama were hit harder than the Tuscaloosa area; the damage is beyond description.

    Bookmark   May 10, 2011 at 11:48AM
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susanbf714 - may I ask how often you have to spray with the dish soap? I'm having an awful time with horntail worms and I'd love to try that technique, just want to do it right!

    Bookmark   August 10, 2011 at 8:36AM
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The "dish soap" used today is not soap but detergents, not your grandmothers soap which was probably homemade by rendering animal fats and then mixing that with lye. You can still buy soap, you just need to watch what you do buy. Mix 1 teaspoon of soap in 1 quart of water to make an Insecticidal Soap. Spray as needed because it is a contact poison and spray when the sun will not cause damage to the plants leaves, like early morning or late evening.

    Bookmark   August 10, 2011 at 11:49AM
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I have seen Dawn used in lots of DIY remedies. What about using Dawn as a surfactant when spraying plants?

    Bookmark   August 6, 2014 at 11:10AM
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DMForcier(8 DFW)

I like Sevin dust. It does what it claims to do and sometimes you need it.

But I have never used it on my pepper plants. I've never needed it, and you DON'T use a broad spectrum killer as a preventative! It kills everything, including the insects that are keeping your pests under control.

Use of Sevin as a preventative may actually cause the problems you are trying to prevent.

Otherwise I like what you have to say. Thank you very much, susan.


    Bookmark   August 6, 2014 at 12:38PM
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Dawn Dishwashing Liquid is not even called a soap by the manufacturer because it is a detergent and not a soap. although the FDA dropped the differentiation some years ago.
Spraying broad spectrum poisons such as Carbaryl (Sevin) in the absence of the target insects is not environmentally responsible. Since things like Carbaryl kill any insect it contacts many beneficial insects are killed if it is sprayed, dusted, or otherwise used unnecessarily.

    Bookmark   August 7, 2014 at 6:39AM
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I use Murphy's Oil Soap to make my insecticidal spray.

    Bookmark   August 7, 2014 at 6:25PM
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I've avoided Sevin for several years and when I dig in the garden I have the big worms they call around here " night crawlers" when I used Sevin the worms were few now they are many . I do use the dish soap treatment for the squash bugs I've also found that companion planting radishes and letting them bloom repels a lot of insects the seed pods are also very edible stir fried or raw , My sweet corn that had some radishes planted next to one end had no corn ear worms in the three rows on that end so my second crop I sowed radishes in every row so will update at harvest time if it helped with that.

    Bookmark   August 7, 2014 at 6:48PM
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Most all "liquid dish soaps" are detergents, not soap. From dictionary. com, "noun
1. any of a group of synthetic, organic, liquid or water-soluble cleaning agents that, unlike soap, are not prepared from fats and oils, are not inactivated by hard water, and have wetting-agent and emulsifying-agent properties.
2. a similar substance that is oil-soluble and capable of holding insoluble foreign matter in suspension, used in lubricating oils, dry-cleaning preparations, etc.
3. any cleansing agent, including soap.
Compare anionic detergent, cationic detergent, synthetic detergent."
Soap is made by reacting a fat, animal or vegetable, with an alkali, usually lye. For organic growers detergents, synthetic products, are not acceptable to use.

    Bookmark   August 8, 2014 at 7:02AM
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so if you do spray the plants with dish soap mixed with water, how often do you need to do that in a week?

    Bookmark   last Thursday at 11:24AM
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That depends on the insect problem. However, spraying any insecticide, even insecticidal soap, once a week may mean there is a larger problem that needs to be addressed.

kimmq is kimmsr

    Bookmark   last Friday at 3:33AM
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ken_adrian Adrian MI cold Z5

kimm ... i am surprised ... we gotta get you up to speed ... its been a long cold hard MI winter.. eh????

no matter what you use.. chem or organic.. you spray ONLY when you have a problem to attack ...

first you fully ID the problem ... including its life cycle [its of no use to kill all the adults.. if they laid eggs.. or your problem will not go away .. and this is usually where you need to follow up on the solution] ...

then you ID the plant .. and its tolerances ...

then you spray accordingly ...

and observe from there ...

soaps.. are instant kill products... they are not preventative ... so there is no use.. to spray your whole garden for the heck of it .. besides killing to many GOOD THINGS ... you might then destroy natures balance .. do not think car wash here ... and think its somehow to your advantage ... to be sparying once a week for no reason ...

finally .. reread all the answers above ..... DISH soap is a detergent.. NOT A SOAP .... though some may have success with such .... i am sure many a plant has died for such ....


ps: regardless of the impact on green leaves ... spraying most flowers themselves.. with soap/detergents ... will probably.. destroy the flower itself ...

    Bookmark   last Friday at 7:51AM
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Ken, if you look hard enough you can find dish soaps that are soaps, although most are detergents. You do need to read the label, carefully.

kimmq is kimmsr

    Bookmark   19 hours ago
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ken_adrian Adrian MI cold Z5

i figure its easy to tell them to go buy a real hort soap.. rather than rely on them to carefully read a detergent label .. lol ...

but i was suggesting a true IPM regimen .. rather than just washing down her plants.. willy nilly ...

they arnt children.. they dont usually need to fed.. and they surely dont need to be washed.. for the sake of it ... eh???


    Bookmark   13 hours ago
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I agree with Ken on the amount of spraying mine was against squash bugs it took a daily egg search masking tape works great on getting the eggs off of the leaves without hurting them I would have a squirt bottle with a soap mix and hit the adults and nymphs but at one point to get the hatched and adults I used a hose end sprayer and I called it nuking the squash and pumpkins but it has only once but did it very late to avoid any bees I'm sure I killed some good bugs but it was needed to gain control

    Bookmark   8 hours ago
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