Dawn dish detergent, dish detergent for pests

Why I Don’t Use Dawn Dish Soap For Pests

The internet can be very helpful and… it can be very harmful. It certainly is often frustrating. For instance, on social media one frequently encounters questions such as: “I noticed some bugs on my pea plants. What can I spray to kill them?” This seemingly innocuous question will produce a regular maelstrom of conflicting advice from people of varying levels of experience and knowledge.  The use of Dawn dish soap in the garden, to kill pests, will invariably be presented, and that, as a harmless, organic way to kill “whatever ails” your garden. I have a number of problems with this approach. First…

Dish detergent is in no way organic.

There are various definitions of organic, but really, no dish detergent you purchase in the grocery store will fit any of them. Personally, I don’t try to squeeze myself into an organic gardening label as I don’t particularly trust organic standards. Still, let’s just dispose of the misconception. No dish detergent is actually organic. Dawn Dish Soap will kill fleas on your dog, but it might hurt your plants. 

Dawn dish detergent might hurt your plants

Some of the recommendations I’ve seen use such a concentration of detergent that I’m pretty sure it would burn the plants. It’s kind of like the time I accidentally smeared hair conditioner on my face, thinking it was body cream. Within a few hours I had peeling skin. A certain  concentration of  dish detergent solution will BURN the plants’ skin, in some cases killing the plants. Most often I’ve seen it recommended for dealing with aphids, yet aphids can be wiped out with nothing more than a blast of pure water. Once they’re knocked off the plant, they fall to the ground, and most of them die before they can get back up. So why risk using soap?

aphids, aphids with ladybug larva
Dawn dish soap will indeed kill aphids, yet notice the other “bug” in the picture, on the right? That’s a ladybug larva eating aphids. Dish soap kills them too. “Ochrosia mariannensis” by Lauren Gutierrez is licensed under CC BY-ND 2.0

and finally,

Using Dawn Dish Detergent in the Garden Will Kill Beneficial Insects

For a related article see Insecticides Favor Pests. Dish detergent solution is basically the same as using a pesticide in the sense that it kills everything with which it comes in contact. It works because it smothers the insects, closing down their trachea, which for insects are found in their skin. They breath through their trachea. You can hardly spray this on your garden and not kill beneficial insects as well. Then, because the beneficials reproduce more slowly than the pests, in short order, you’ve made the situation worse.

So what should one do about garden pests?

  1. Remember, not every insect you encounter is hurting the garden. Don’t assume that you have to do anything.
  2. Remember that for a healthy ecosystem in the garden, some pests have to exist. There is an acceptable level of pest damage for the one who thinks about long term health and productivity.
  3. With many pests, one can hand pick, dropping them into a coffee can containing water and a little bit of vegetable oil. This process is selective and can leave the predators alive to catch up with the pests.
  4. I once dealt with a huge plague of grasshoppers by going out before dawn and using a shop vac to vacuum them off of their roosts before they got awake enough to flee. Then I dropped the vac in my deep freeze until after work before feeding them to our poultry.
  5. In many cases it’s okay to allow a few pests to live, if not simply for the purpose of feeding beneficial insects.
  6. One can even purchase and release beneficial insects in the garden. Arbico Organics is my favorite company for obtaining beneficial insects.

Do you have a favorite, selective method for dealing with garden pests? Share with our readers in the comment area below.

3 thoughts on “Why I Don’t Use Dawn Dish Soap For Pests”

  1. That was an exceptionally good article about using Dawn dishwashing soap or any kind of soap on your plants. Soap of any kind is a surfactant and will break down the protective waxy coating on your plants, allowing them to dehydrate very quickly and allowing disease to penetrate the surface. (It would be similar to peeling off layers of your own skin, then sunbathing the rest of the day.) Surfactants are used in weed killers, to break down the waxy barrier, so the poison can penetrate the leaves more readily. (God put the waxy barrier on plants for a reason).

    Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. While good for removing dirt from your hands, not so good for removing insects from your plants.

  2. Thank You George! Great write up. I am not sure, why people think there is something wrong with picking pests off their plants… or hoeing to get rid of their weeds.

    Moni

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