Best Organic Insecticidal Soap for Tomato Plant Pests

Why I Started Using Insecticidal Soap on My Tomato Plants

When I first started growing tomatoes, I thought watering and sunlight were the only things I needed to worry about. Then came the aphids, whiteflies, and even spider mites — all setting up camp like my tomato plants were an all-you-can-eat buffet. I was losing leaves left and right, and some of my plants were curling so badly, I wasn’t even sure they’d make it.

At first, I panicked. But after a little digging (pun intended), I learned these weren’t diseases — they were pest issues, and they were treatable. That’s when I found something that changed everything: insecticidal soap. More specifically, this one right here that I now use religiously.

If you’re seeing curled, droopy, or stressed-looking tomato leaves, especially early in the season, it might not be what you think. I break that all down in this article about curling tomato leaves and what to do first — and trust me, insecticidal soap is often part of the answer.

What Makes This Insecticidal Soap Actually Work

This isn’t just some DIY dish soap recipe that might help in a pinch — it’s a real solution. The Safer 5118-6 Insect Killing Soap uses potassium salts of fatty acids, which might sound fancy, but here’s the deal: they break down the soft outer bodies of bugs like aphids, mites, and whiteflies. No chemicals. No residue. Just a clean, targeted takedown of garden pests.

It’s OMRI listed for organic gardening, so you can safely use it on your edible crops without worrying about what you’re spraying on your food. That’s a huge win for me. I grow all my tomatoes in a mix of raised beds and grow bags, and this stuff plays nice with both.

Plus, it doesn’t interfere with my best soil mix for tomatoes — which is crucial, because healthy soil is half the battle.

The Bugs This Soap Knocks Out Cold

Let me just list the pests I’ve personally sent packing with this stuff:

Aphids – They suck the life out of your plant. This spray makes them vanish.
Whiteflies – Tiny, but man do they multiply. This handles them in a day or two.
Spider Mites – If you see webbing, this is your new best friend.
Thrips – They’re tiny but destructive. This soap takes care of them fast.
Mealybugs & leafhoppers – Soft-bodied bugs don’t stand a chance.

If your tomato leaves are curling, puckering, or showing weird patterns, there’s a good chance pests are involved. That’s why I always tell folks to try insecticidal soap first, just like I recommend in this guide to tomato leaf curl.

How I Use It Without Harming My Tomato Plants

I’ll be honest — when I first sprayed something on my plants, I was a little nervous. Would it burn the leaves? Would it mess up the fruit? But I’ve now used this Safer insecticidal soap on everything from cherry tomatoes to beefsteak varieties with no issues at all — as long as you use it the right way.

Here’s how I do it:

Early morning or evening only – Never spray during the heat of the day.
Spray directly on bugs – This works on contact, not as a lingering pesticide.
Undersides of leaves matter most – That’s where the pests hide.
Wait and watch – I usually see results in 24–48 hours.

And just to be safe, I’ll test it on a single plant before going all in. It hasn’t failed me yet, especially when combined with strong airflow and good watering habits like I talk about in this watering guide.

It Fits Right Into Organic Gardening

One of the big reasons I switched to this stuff? It’s OMRI Listed, meaning it’s been approved for organic gardening. I’m not growing tomatoes just to spray them with who-knows-what — I want clean fruit I can eat right off the vine, and that’s what this allows me to do.

It also works perfectly in combination with other organic gardening tools I use, like:

Organic tomato fertilizers to feed the plants
Mulching methods to reduce pest pressure and moisture loss
DIY trellising to keep foliage off the ground

I want all of it working together — healthy soil, pest control, airflow, water, and support. This spray is just one part of that system, but it’s made a huge difference.

When to Reach for This (and When Not To)

So when should you pull this out of your garden shed? Here’s what I’ve learned:

Use this insecticidal soap when:

You see tiny green, black, or white bugs clustering on new growth.
Leaves are curling or puckering and you’ve ruled out watering issues.
There’s webbing under your leaves (hello spider mites).
You want a gentle but effective fix that won’t ruin your harvest.

Avoid spraying if:

It’s a scorching 90-degree day — wait until early morning or late evening.
The plant is already very stressed (go gentle and start with a test).
You’ve already drenched the plant with something else (don’t overdo it).

For most pest problems, this insecticidal soap is the first thing I try, and it’s almost always the last thing I need.

What Pests It Actually Works On (and What It Doesn’t)

After testing this soap across multiple tomato-growing seasons, I’ve learned what it’s great at — and where it falls short.

Here’s what it kills well:

Aphids – A couple of sprays and they’re toast.
Whiteflies – You’ll see fewer buzzing around almost immediately.
Spider mites – It won’t fix damage already done, but it stops the spread fast.
Thrips – These tricky pests drop off when hit directly.

But let’s be real — this won’t work on everything.

If your tomato plants are being chewed to shreds by fat green caterpillars, you’re probably dealing with hornworms.And this spray won’t touch them.

That’s when I switch to the big guns 👉 Sevin Insect Killer Concentrate: The Hornworm Killer That Works

You can also check out this full guide where I walk through how I spot, remove, and prevent hornworms (without losing my mind):
🪱 How to Get Rid of Hornworms on My Tomato Plants Without Losing My Mind

How Often Should You Spray It?

From my own experience and what’s on the label:

Every 5–7 days for active pest outbreaks
Every 10–14 days as a maintenance spray
Spray directly on the bugs — it only works on contact

Always spray either in the early morning or late evening to prevent leaf burn. I learned that the hard way one summer afternoon…

This stuff doesn’t replace a full garden care routine, but when paired with proper support, watering, and fertilizing — like these methods here 👉
🌱 How to Grow Tomatoes Faster – 10 Proven Tricks That Work — it helps keep pests under control before they explode.

So…Should You Keep This In Your Garden Shed?

Without hesitation — yes.

Safer Insecticidal Soap is now a permanent part of my tomato-growing toolkit. It’s organic-approved, effective on soft-bodied bugs, and doesn’t make me worry about kids or pets around the garden.

If you’re growing tomatoes and want a gentle but solid defense before things get out of hand, here’s where you can check it out:
👉 The Insect Soap I Personally Recommend for Tomatoes

And if hornworms show up? You know what to do now 😤.