Will Dawn Hurt Tomato Plants

Washing your tomatoes or even doing home remedy garden treatments is something every gardener wants to try. Dawn soap is one of those that you see mentioned often in the gardening space, but will Dawn hurt tomato plants?

Despite some fears, Dawn is a detergent, not a soap, and it’s not usually harmful to your tomato plants. 

At least Dawn isn’t harmful when it’s used properly. 

Plus, the good news is that it’s cheap, you don’t need much of it, and it’s a versatile tool that can help keep your tomato plants healthier so you can get a bumper harvest. 

Let’s dig into how you can use Dawn to help your tomato plants: 

How To Use Dawn Dish Soap On Your Tomato Plants

You might want to use Dawn dish soap on your tomato plants for a few different reasons. Most people use it for mold control or to deal with some common pest insects. 

We’ll get into more detail about how you can use Dawn soap on your tomato plants in a bit. In general, Dawn is used for three primary purposes: 

1. Killing insect pests
2. Deterring insect pests from getting on the plant
3. Removing mold and mold spores

Before we get into more detail about the uses of Dawn, let’s talk about how to use Dawn dish soap without causing problems for your tomatoes: 

Is Dawn Safe For Tomato Plants? 

Yes and no. Dawn is safe to use on tomato plants, but you do need to dilute it and be relatively careful about how you use it. 

That’s because Dawn is technically a detergent like most dish soap. It can harm plants in strong concentrations, especially when they’re used more often than they should be or when you’re putting large amounts of the detergent directly on the plant. 

Much like a little bit of fertilizer is perfectly safe and beneficial for your tomato plants, but too much fertilizer can cause chemical burns and even kill the plants; Dawn is usually safe, but only in the right concentrations and with breaks between applications. 

As a rule of thumb, you should combine no more than 1-2 Tablespoons of Dawn dish soap with 1 gallon of water for use on your tomato plants. The scent of the Dawn doesn’t matter, but you should use less of the soap if you buy an ultra-concentrated or high-strength version. 

Should You Test Dawn Soap On Tomato Plants Before Using It? 

Testing your Dawn soap solution on tomato plants before you use it on the whole plant or the whole group of plants is a good idea. 

To test Dawn soap mixtures, regardless of whether your mixture is just Dawn and water or if you have additional additives mixed in, you’ll want to spray a small amount of the solution on 2-3 leaves near the bottom of your tomato plant, trying not to get too much on your stem. 

That’s important because if the solution does damage your tomato plants, which is rare if you’ve diluted the soap enough, you don’t want to damage the stem. The plant can probably handle losing the bottom leaves if it’s at least 12 inches tall, but it may not be able to recover from stem damage in the same area. 

You should also consider testing more than one tomato plant if you’re growing more than one variety or even just different cultivars of tomatoes. 

You should test your Dawn solution on at least one plant from every cultivar of your tomatoes, not just one plant, and assume it’s okay for all the others. 

So even if you have two slicing tomato plants growing, if they’re different cultivars, you should test both plants, not just one. 

Leave the soap mixture in place for at least 48 hours and inspect for any yellowing or brown spots. If the leaf is undamaged, your mixture is safe to use. If there are yellow spots, dilute the mixture further and test again. 

What Is Dawn Dish Soap Used For On Tomato Plants? 

Okay, now that you know more about how to use Dawn safely, let’s talk about the specific uses for Dawn on tomatoes. 

Getting Rid Of Powdery Mildew And Fungal Growth

Powdery mildew is one of the more common diseases in vegetable plants, including tomatoes. While it might not be as harmful as some other diseases, it can still cause problems for your plants and your tomato harvest. 

Getting rid of powdery mildew requires two things. 

First, you must get rid of the powdery mildew on the plants. That’s easy; you can wipe it off with a sponge or a paper towel. 

However, the second part is a little harder. The second thing you need to do is get rid of the fungal spores produced by the mildew because it’s the spores that let it spread. 

Make Insecticidal Soap

Insecticidal soap is one of the most useful tools in your garden, especially if you aren’t interested in using other harsher pesticides to control insects. 

The recipe is simple. Add approximately one tablespoon of Dawn and two tablespoons of any cooking oil to 1 gallon of water, and put the resulting mixture in a spray bottle. Spray the mixture on any insects you want to kill, and use up to 1-2 times a week to help control infestations. 

The soap kills the insects it fully coats, but it’s still a great way to reduce the population of pests in your gardens and, over time, can eliminate some of the most harmful pests.

Get Rid Of Sooty Mold And Mold Spores

Sooty mold is one of the reasons having aphids can be such a problem on your tomatoes. However, with Dawn helping, you can quickly deal with the aphids causing the sooty mold and the mold itself. 

Use the insecticidal soap recipe we listed above. Then, about 2 hours later, go back and spray down or wipe down the plants to get rid of the dead aphids and the mold. 

Eliminate Difficult Scale Insects

Scale insects can be difficult to eliminate because they latch on to plants and then take advantage of the hard protective armor on their backs to stay in place. 

Spraying down a plant, like you might to deal with aphids and beetles, generally doesn’t knock these scale insects loose. 

But, if you make insecticidal soap, that does work. A small dab of soap on the back of the insect will also remove it, sometimes faster than insecticidal soap. 

Make sure you’re careful not to get any of the Dawn directly on the plant when you choose that second option. Dawn might not harm animals, but it will burn your plants. 

Stop Whitefly Infestations

Whiteflies are a stubborn and fast-breeding infestation too tiny to be effectively blocked by many screens. 

Instead, spray your plants with insecticidal soap 2x a week until the infestation is gone. 

Get Rid Of Mealybugs

Still, need another insect pest Dawn can take care of? Well, mealybugs are that pest. 

There are many ways to potentially deal with mealybugs, but, like many of the other insect pests in this article, insecticidal soap made with Dawn is one of the gentlest and most effective tools.