Neem oil. Extracted from the seed of a neem tree growing in South Asia. Smells a little like garlic. Cold-pressed if you want to be fancy. Sometimes pure, other times diluted. But no matter how you look at it, this oil is amazing.
Not only an insecticide, neem oil goes above and beyond in ridding our unwanted creepers. Mealybugs, aphids, whiteflies, Japanese beetles, scale, thrips, spider mites (I know, not actually an insect – closer to a spider), and leafhoppers don’t stand a chance against the might of this simple oil. Neem oil fights insects in three ways:
- It’s an antifeedant. It means when the insect ingests treated leaves, the oil inhibits its taste receptors. It doesn’t recognize the leaf as food so it moves on. Isn’t that cool? It tricks insects into thinking the plant isn’t a meal. Even better, since pollinators don’t eat leaves, the oil doesn’t pose a risk to them at all.
- It messes up their hormones. This is important because without the correct hormones, insects can’t continue through their life cycles – they can’t molt, they can’t pupate, and they can’t lay eggs.
- The oil coats soft-bodied insects like aphids. While this doesn’t work on things like beetles, it will work on lots of insects to inhibit offense on your plants.
How do you apply neem oil? Well, the biggest thing to remember is spray plants in the morning or evening. This does two things. It protects the leaves from sunburn, which is a thing even in the Pacific Northwest. And it means pollinators aren’t out. Remember, pollinators don’t eat leaves, but they could still be affected by the hormone and smothering attacks. So, wait until it’s cool outside and everyone’s asleep.
When you spray a plant with neem oil, you want to focus on the insects themselves. You want to make sure any unwanted bugs are drenched in it. You will also need to repeat spraying every few days until the insects are gone. The benefit that neem oil doesn’t harm the environment also means it doesn’t stay in the environment very long.
If you buy pre-mixed neem oil, you can just spray directly on the plants. If you buy concentrated neem oil, you need to mix it with water and a surfactant. You can buy surfactants in the garden center, but you can also just add a drop or two of dish soap. It breaks the surface tension of the oil, spreading it out to cover more area and stick better. It’s a pretty cool science thing – l recommend reading about it.
Bonide, Captain Jack's Neem Oil Spray, 32 oz
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Bonide, Captain Jack's Neem Max Concentrate
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So – insects stop eating, stop cycling, and stop hanging out on your plants. Those are the three insecticidal properties. But neem oil has a few other tricks. Not only is it good at killing bugs, but it’s also good at controlling fungi. Let’s take a look at that.
Powdery mildew, black spot, scab, and blight cause trouble in a garden. While many will say it gets rid of these problems, it doesn’t work quite that well. Once it’s there, it’s almost impossible to get rid of. And that’s true even of neem oil. It can’t “cure” these diseases, but it can keep them from spreading. Going back to the idea of coating leaves with oil, neem oil creates a protective layer over healthy leaves. This way the fungal spores can’t take hold. If you spray a plant at the first sight of powdery mildew (I always get it on my squash leaves), or any other fungal infection, it will keep it in check.
And neem oil isn’t just for veggie gardens. It can be used as a dormant spray on perennials to kill overwintering insects and eggs. It can be used in orchards to protect leaves from sharing fungal infections like rust. It can also be used inside when house plants develop white flies or fungus gnats.
All in all, there are few products better than neem oil in a garden. It stops insects in three ways, it protects leaves from fungal infections, and it is harmless to pollinators. The only drawback I can think of is the need to respray regularly. But even that’s not a bad thing. Neem oil makes you pay attention to your plants. It helps you recognize their needs. And we all know that gardeners are always looking for another excuse to hang out in the garden. At least, I know I am.
