How I deal with aphids in the greenhouse and garden

There are certain topics (or questions) that I can always expect at certain points throughout the year, and May until August is always about aphids or whitefly. usually, it’s how can I get rid of “said pest”.

OK here’s the honest answer – you can’t. I’m sorry but this is part of the ecosystem that your garden is in. You just can’t stop nature and hopefully, when we ask these questions, we don’t really mean that we want to. Because let’s face it, if we get rid of aphids then there are other creatures we’d lose too because we are messing with the ecosystem. Think about animals that are no longer with us because of this. In Scotland, we have a huge problem with deer. There are no longer any natural predators which manage their numbers (because we got rid of wolves and lynx) so now deer are such a pest that they have to be culled each year to control numbers. The same reaction would happen if we got rid of aphids. Think of all the animals that eat them and rely on them for a food source.

BUT…

we can manage them in our garden and greenhouse to help stop them from overrunning the garden and making too much damage.

So let’s start with the obvious one. Let’s talk about what they actually are.

Aphids and white flies are tiny, soft-bodied insects that feed on the sap from your plants. I am going to just use the term aphids from now on, but you know I’m talking about all these little suckers. They come in many colours, green, black, yellow even pink. They usually go for the soft new growth and, to be honest, they don’t do a whole heap of damage, but, there’s that but again. One or two aphids are not an issue but they multiply VERY quickly and that’s where you get problems.

An infestation of aphids can do a lot of damage by sucking the sap from your plants and weakening it to the point where it can die. They also, because they penetrate the plants and move around on them, spread disease from one plant to another, one garden to another. And they secrete a sticky, sweet substance called honeydew which moulds love to grow on.

You will quite often see ants on your plants, and usually, within a matter of days, you will also see aphids. This is because the ants, who don’t actually do any damage, actually farm aphids. Yes, you read that right! Ants eat the honeydew, and so they go and collect aphids and bring them to particular plants in numbers and protect them from predators like ladybirds and lacewings so that they can eat the honeydew. Did you think only humans farmed animals for their own benefit?

So, with all this in mind, I said you could manage the aphids.

You can obviously buy a heap of sprays which will kill them. However, if you are trying to grow without adding unwanted things to your garden, here are my three ways to deal with them.

Get them early

The first is for whenever you see any aphids. You’ll often see me do this in videos but it’s just to squish them. If you are seeing one of two just squish them right then and there and it stops that one or two from multiplying. This should always be your first line of defence, don’t wait. They multiply very, very quickly.

Obviously, if you don’t manage to catch them early and they multiply then this becomes a never-ending and gruesome task.

Water

Believe it or not, a simple jet of water is a fantastic way to deal with them. Put your hose on the jet or use a spray bottle for more delicate plants and just blast those little suckers right off.

What happens is that you knock them off the plant and many will be killed in that action or subsequently once they are away from the safety of numbers (and ants).  I sometimes hear people telling me that this doesn’t work, and again I remind you that we are managing numbers not getting rid of them. So this isn’t a one-time thing, you have to do this a few times in frequent succession and you will find each time you do, the numbers will dwindle.

This is my number one way to deal with things.

Soap Spray

Soap spray is a great way to kill aphids. It works by coating their bodies (remember I said soft-bodied) and basically doing 2 things. It suffocates them because soft-bodied insects breathe through their skin and the oil in the soap coats their bodies and stops them from breathing, and secondly, they become dehydrated. So they die.

OK now this is the simple explanation, but I just want to make a point of saying this. I’m not going to go into a big explanation here because I’ve already made a lengthy video about the subject but… soap spray is not natural, it’s a traditional remedy, not a natural one because it is not something which is normally in your garden. If you use this be careful because it can affect the insects including the beneficial ones and it can damage your plants and it can absolutely decimate water life.

My main piece of advice is to be very careful about the soap you use because almost all modern soaps are no longer actually soap, they are detergents or degreasers but the same words and language are still in use so people misunderstand this. Do not use dish soap (washing up liquid).
Again, I won’t go on but here is the video if you want to hear me lecture you:  https://youtu.be/jEdjPpyNpHc 

To use soap spray, you basically spray the insects, not the plant. But again, it’s not a one-off application, you will have to do this every day for a few days. As it only affects the insects it touches so won’t affect new ones to arrive after or any newborn. It’s best to spray first thing in the morning or in the evening when the plants aren’t stressed already by the heat and light of the sun.

Neem Oil

Neem oil is another option in terms of making a spray to use. It works slightly differently in that you spray the plants and it works when the insects eat the plants. Azadirachtin, the active element in neem oil affects the insects’ bio cycle and stops them from eating and reproducing. So it is slower to work than soap spray but will affect a larger range of pests including caterpillars, earwigs and chewing bugs.

Again be careful when using this as too strong a solution can damage your plants and it can affect other friendly insects if you spray it willy-nilly.

Video about how I use it: https://youtu.be/xRUnpbXLgcw 

I’m going to take this chance to clear up a misunderstanding about neem oil. Neem oil itself isn’t banned in the UK as many people seem to think.

There are always a lot of rumour mills on the internet and quickly someone’s misunderstanding becomes an urban fact. So…

The ingredient that makes neem oil effective, azadirachtin, is a controlled substance in terms of agriculture (in other words farming or market gardens, commercial homestead etc) because in very high quantities (like those used in farming) it may cause health issues in people and animals. Think massive spraying of crops using the extracted concentrated azadirachtin. The quantities we use in gardening and the fact that we are using whole neem oil and not an artificially extracted and concentrated ingredient means it is safe for use.

However, check your local law before you try to buy any.

My last recommendation is more long-term: plant a garden that attracts beneficial insects which will manage your aphid population

This is my last suggestion as obviously, this one takes time but it is 100% organic, ethical and sustainable. Find out what your local beneficial insects are and plant the things that attract them.

I don’t recommend buying insects like ladybirds through the post. Namely for these reasons:

• it’s cruel to put animals in the posts
• they will arrive weak, and dehydrated, some will be injured and some will be dead due to the handling and movement of them being posted
• if your garden isn’t already planted up to attract these insects naturally, the ones you buy won’t stay, they will leave shortly after.

Again this is a long topic for discussion, too long for this post but I’d recommend planning for the future and planting your garden for the beneficial insects in the hope of attracting them to your garden and encouraging them to stay, but that’s for next year.

However, it does mean you have time to do a little research and find out all about them this year so you are prepared come sowing season 😀