Using neem oil in the garden to combat pests

In our previous blog post, we talked about the timeless pest control method of soap sprays for the garden. Today we are going to look at its sister remedy, neem oil. Again, it’s one of those traditional gardener’s remedies passed down through the generations and is still used in lots of organic gardens today. But as with soap sprays, modern living has had an impact and unfortunately, we may find that the neem oil or even prepared neem oil spray we bought, isn’t cutting the mustard (so to speak).

So first things first, for those of us who are new to these garden remedies…

What is neem oil and why use it?

Quite simply, neem oil is an oil extracted from the seeds of the neem tree. It’s a natural pesticide and has anti-fungal and anti-bacterial properties. So really useful for combating those pests in the garden. It’s different from the soap sprays in the way that it combats the beasties, hence why I wanted to talk about the two things separately, giving you a chance to find out more and chose the right solution for your garden problems.

However, much like the soap I discussed in the previous blog post, neem oils are not all equal. Neem oil is actually used in more than just gardening, it is used in the beauty industry too and so you may find that you can buy many different types of neem oil product. Unfortunately, some of these are actually no use to us as gardeners.

What to look for when buying neem oil

The essential compound in neem oil which combats beasties is called azadirachtin. You want to make sure you buy a neem oil with a high concentration of azadirachtin. This might sound obvious but neem oil is extracted from the seeds in many different ways and they all affect the amount of this in the finished product. We are looking for 100% cold-pressed neem oil, this is the method which has the highest concentration in the finished product.

Also be aware of products labelled as extract of neem oil, again, this is not 100% pure neem oil and may not have enough azadirachtin.

So how does neem oil work?

Well it actually works in a few different ways. Firstly, it smells absolutely foul. I mean seriously. I left a spoon in the sink this week which I had used with neem oil and when Kate added hot water to the sink to do some dishes, I could hear the shouting and numerous expletives from the upstairs bedroom. It’s that bad.

So as you can imagine that foul smell is one way it works, it actually repels a lot of insects and people.

It is also what is called a systemic insecticide. Meaning that once you spray it on the leaves, or if the roots absorb it, it is then taken up into all areas of the plant, meaning that any bug who chews your plant is affected. This is also handy as it’s hard to get to the larvae which attack plant roots, so this is great for things like beetles, earwigs, caterpillars etc that chew your plants.

Now, this is where neem oil works differently from the soap sprays. With the soap sprays, they kill the soft-bodied insects through contact and it works quite quickly. The neem oil, however, takes a bit longer to work. What it does is to actually affect the hormones of the insect causing them to stop eating, stop mating and it also affects their growth.

Again, the reason I wanted to talk about this method (as well as the soap sprays) is because when diluted down and used in this way, it isn’t harmful to other garden life like pollinators, birds, your pets etc unless you spray it directly onto them, same warning as with soap sprays, don’t spray this on things you don’t need to. And it is also not toxic to us or our pets etc when used in this way. Obviously it goes without saying, don’t drink it or rub it undiluted all over your face…..

How to make up a solution of neem oil

So let’s talk about making up and using a solution. The first thing I want to mention is that there are a few common myths out there and I want to clear them up. Firstly, you do not add neem oil to your soap spray. It doesn’t create some sort of two in one extra beneficial spray. All you’ll do is introduce more foreign things to your plants and risk stressing them out. Instead, choose which type of spray you are going to use based on what you are trying to achieve. Soap spray for one type of pest, neem oil for the others.

So as always, make a diluted spray first and test it on a few leaves to make sure you don’t do any damage. Use this method to adjust the recipe to suit your needs.

I make this up in small batches as it doesn’t actually keep very well, and there is no point making a large batch if you are just going to have to throw it away. I usually make a litre at most. There are also two recipes I use, depending on how I am going to use it.

To spray onto plants when you have a problem

Start with one litre of warm water – warm is essential as proper neem oil will actually solidify and you need the warm water to help bring it back to oil.

To my one litre of warm water, I add two teaspoons of neem oil. Now obviously as this is an oil, it won’t actually mix with the water. You can shake it up but it will very quickly start to separate again.

So in order to help it all come together, we add a tiny bit of our soap. Now I really do mean tiny, we aren’t making a soap spray, we are JUST using enough to help the oil and water mix.

So I do this by adding about a half teaspoon, then shaking the solution up. You will see that things do start to separate out, with the oil floating to the top, this will happen, but you want it to take about 30 seconds or longer for this to happen, giving you enough time to spray your plants.

If your solution is separating too quickly, add another half teaspoon of your soap. I find for one litre of warm water and two teaspoons of neem oil, just under a teaspoon of soap seems to do the trick.

A soil drench or as a maintenance spray

Now what you can also do is to make something called a soil drench. This is great to combat pests in the soil, like fungus gnats (we sometimes have these in our peace lilies). You can also use the spray to deliberately spray more than once, to maybe just keep pests under control. In both these instances, I would make a weaker solution, usually just the one teaspoon of neem oil in a litre of warm water.

So there you go, neem oil and how to use it to combat pests.