Although both are often suggested to control various pest issues on both indoor and outdoor plants, isn’t it time for an insecticidal soap vs neem oil comparison? After all, they each have distinct uses, benefits, and drawbacks, and once you understand those, you’ll know just which product you should reach for and why. In this article, I’ll discuss what both of these products are and share some valuable insight into their differences.

As you’ll soon come to learn, which one you ultimately choose depends on the types of pests you’re dealing with and how serious your infestation is. You might even decide to keep both insecticidal soap and neem oil on hand. One is an affordable on-contact killer. The other has some extra utility but costs a little more. Let’s dive in.

Why opt for natural pest control products

One good thing about making decisions around insecticidal soap vs neem oil is that both of these choices are, environmentally speaking, fairly benign compared to synthetic pest controls. Unlike most natural products, some manmade (aka synthetic) pesticides can harm people, pets, and non-target mammals, birds, and more. They can also pollute area waterways and subsequently affect sensitive amphibians and other aquatic creatures.

Finally, because synthetics act on many different kinds of insects and they can remain in the environment for longer periods, they can also put a dent in beneficial bug and pollinator populations. Reaching for more environmentally friendly pest control options (like the insecticidal soap and neem oil featured in this article) is always a better approach.

What is insecticidal soap?

Insecticidal soap is the product of a chemical reaction between fatty acids and potassium hydroxide, a strong alkaline substance which readily absorbs moisture. The resulting soap is incredibly drying to soft-bodied insects. When sprayed directly with insecticidal soap, the outer coats of these target insects are damaged, leading to dehydration or suffocation.

Benefits and limitations of insecticidal soap

As you consider insecticidal soap vs neem oil, there are some specific benefits and drawbacks for each. Regarding insecticidal soaps, they tend to be a little less expensive than neem oil products. However, they only work when they come into direct contact with soft-bodied insects like aphids, sawfly larvae, scale insects, mealybugs, thrips, lacebugs, whiteflies, and spider mites—and only then while the spray is still wet.

What is neem oil?

Before we can explore the benefits and limitations of neem oil, it helps to know where it comes from and how various neem oil products differ from one another. Have a bottle of canola or safflower oil in your kitchen pantry? These are made from the processed, ripened seeds of those respective plants. Similarly, most neem oil comes from the oil-rich seeds of Azadirachta indica—a tropical tree native to India and parts of Asia.

From its flowers, fruits, and leaves to its bark and seeds, every part of the neem tree contains hundreds of chemical compounds, many of which act as a natural insect repellent. Pesticidal neem oil comes in a few different forms. You may find pure, cold-pressed neem oil concentrate. This can be diluted and applied in a variety of ways.

Sometimes, manufacturers isolate a chemical called azadirachtin from the neem oil and market mixtures containing this potent neem-derived pesticide. Finally, the stuff leftover after the extraction of azadirachtin is also sold as a pesticide. You’ll see it listed as “clarified hydrophobic extract of neem oil” in products like this ready-to-use neem oil spray.

Benefits and limitations of neem oil

In making the case for insecticidal soap vs neem oil, you’ll likely find that there is a time and place for each. Here are some of the distinct benefits and limitations of neem oil in particular. Recall that it comes in a few different formulations—pure, cold-pressed neem oil concentrate, azadirachtin-specific mixtures, and clarified hydrophobic extract of neem oil.

Neem oil can act on a really wide range of insects and it does so in more than one way. For instance, when sprayed directly onto plants, cold-pressed neem oil mixtures and products containing azadirachtin deter pests’ nibbling. Any insects that do ingest azadirachtin-treated leaves, the chemical disrupts certain life stages. This prevents affected insects from reaching adulthood which, in turn, means they can’t further grow their numbers by laying more eggs. Used as a soil drench, azadirachtin mixes can help prevent some fungal diseases and control fungus gnats, too.

Ready-to-use neem oil sprays—especially those containing only clarified hydrophobic neem oil extract—may not necessarily prevent future infestations quite as well as azadirachtin-containing mixtures do. Still, like other horticultural oils, ready-to-use neem oil preparations will kill caterpillars, mealybugs, spider mites, scales, various pest eggs and larvae, beetles, and many other garden pests when they’re directly sprayed with it.

How to use insecticidal soap vs neem oil properly

When it comes to insecticidal soap vs neem oil, keep in mind that both come in concentrates and ready-to-use formulations. For concentrates, follow package directions when mixing and pour your mixture into a clearly labeled spray bottle.

Because some plants may be sensitive to these preparations, it’s best to spray just a few leaves at first, wait several hours, and then check back for signs of leaf burn or damage. Also, because pollinators can be affected by these pesticides, take care to apply early in the morning or later in the evening when pollinators aren’t active.

Effectiveness comparison: Insecticidal soap vs neem oil

How effective is insecticidal soap vs neem oil? Insecticidal soap only affects soft-bodied pests that have been directly sprayed, but it does do the trick quite well. Once dried on plants, it’s no longer active. It is relatively benign to plants, people, and pets, and is easy to use.

Neem oil is effective against both soft- and hard-shelled bugs. Use clarified hydrophobic extract of neem oil as you would an insecticidal soap. Neem preparations with azadirachtin are additionally effective as systemic bug repellents, meaning it is carried within the transport tissue of plants it is applied to, providing longer-lasting pest management.

Choosing the right option for your plants

While there’s still ongoing debate about insecticidal soap vs neem oil, there is a time and place for each. Have an active pest infestation of mostly soft-bodied insects? Spray them directly with an insecticidal soap. Check back in a day or so and reapply as needed.

For large populations of multiple insect types, including scale, beetles, and caterpillars, among others, hit them with a ready-to-use neem oil spray. And to discourage insect feeding on your plants and prevent future infestations, you can dilute cold-pressed neem oil concentrate or a similar product containing azadirachtin and spray onto plant leaves or use as a soil drench. The plant will systemically take up some of the active ingredients and pass them along to insects that eat the treated plant’s leaves.

No matter which product you choose, ALWAYS read the label carefully and follow all instructions exactly. In addition, some products are not labeled for use on specific, sensitive plants, so make sure the plant you plan to spray is on the product’s “safe list.”

Buggin’ out: Final thoughts on insecticidal soap vs neem oil

So, insecticidal soap vs neem oil—which is best? Well, now you know the answer depends on what insects you’re trying to manage and how. Insecticidal soap kills soft-bodied pests on contact, but, once it dries on your plants, it’s no longer effective. Products with “clarified hydrophobic extract of neem oil” listed as their active ingredient work in a similar way, but they do affect many more types of insects.

Hope to prevent further feeding by a wide assortment of insects? Neem oil preparations containing azadirachtin have further value as systemic pesticides. Your plant takes up this natural insect repellent. As for insects that do feed on treated plants? Their lifecycles are disrupted, and they fail to mature.

For more organic pest-control advice, head to these additional articles: 

• Make a DIY cucumber beetle trap
• Bugs in your broccoli? Here’s what to do
• How to get rid of squash bugs
• Common rose pests