How to get rid of aphids on plants – Prevention & Treatment

How to get rid of aphids on plants – Prevention & Treatment

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I’ve discussed scales insects and thrips before, both of which suck the sap out of plants. Scale insects and thrips can be a big problem should they get out of control. However, there is one pest that seems to plague plants more than other pests, they are aphids. These generally include greenflies and blackflies, although there are many other types of aphids, and they are usually selective to one type of plant. This means the aphids feeding on your roses are probably not the same types of aphids feeding on your vegetables.

I have found that controlling aphids early on in the cycle has a significant effect on lowering aphid numbers later on in the season. I have also found that by doing this, aphid numbers are not significant enough to cause much concern and the natural predators are usually enough to control the aphids naturally. That being said, there are a few methods I use to control aphids and you can read about them below.

Aphids are an important part of your gardens ecosystem

Encouraging ladybugs into your garden will help control aphids
Ladybirds feed on aphids so encourage them into the garden

You have no doubt come across aphids at some point. They usually feed on the younger soft foliage of plants, but it’s important to realise they are actually an important part of the garden ecosystem. They provide food for many other insects including our much-loved ladybirds, lacewings and earwigs to name a few. Also, young songbirds like sparrows and blue tits also feed on the aphids.

ladybug  and a ladybug larva that eats a lot of aphids, as many as 200 in their lifetime
An adult Ladybird and a ladybird larva that eats a lot of aphids, as many as 200 in their lifetime

It’s actually the larvae of Ladybirds, hoverflies and lacewings that eat aphids on plants.

If you have aphids in a greenhouse, a great way to control them naturally is by releasing ladybirds into your greenhouse where they are less likely to fly away. Believe it or not, you can even buy them online!

With all this in mind, and to ensure a balanced ecosystem, it’s actually best to control the aphid populations so they don’t get out of control, rather than trying to eradicate them completely. Smaller populations of aphinds don’t usually cause any issues; in fact, you probably won’t even realise you have them.

How to control aphids

Infestation of aphids on rose shoots
An infestation of aphids on rose shoots

The short answer on how to get rid of aphids is to either, manually find or remove them with your fingers. This is fine for smaller populations on individual plants but for larger infestations, spray them with a contact pesticide. This could be horticultural oils or even a homemade mix of soapy water, you also have the option of using a systematic pesticide (bug killer) that kills the aphids and continues to work for months because it’s in the plant’s system and kills the aphids when they suck the sap out.

What are aphids?

Close up of greenfly aphids
Close up of greenfly aphid

The term aphids cover over 500 species but greenfly (as pictured above), blackfly and whitefly, are probably the most common. They look just like tiny flies with small bodies. They are very tiny, I’m talking 1-2mm long so they can be difficult to see, yet surprisingly hard to miss when you get an infestation of them. They can actually reach around 7mm long. What they actually do is suck the sap out of the leaves and stems of your plants, leaving the plants without enough energy to flourish.

Over time, the plants start to wilt, and the leaves begin to curl.

How to recognise whether you have aphids

Look closely at your plants for little flies of almost any colour, including pink, although they are usually green, black or brown. They tend to go around in groups, making them easier to find this way.

Aphids underneath the leaves can be hard to spot
Aphids underneath the leaves can be hard to spot

They hang around on the undersides of leaves, so the trick is to check underneath the leaves, as shown in the picture above. As previously mentioned, the leaves may turn yellow and start to curl, and then drop off the plant. You really need to check plants well because they can hide well.

Another big clue is a sweet sticky substance called honeydew that aphids leave behind. Watch out for a clear, resin-like gel on the leaves. Another sure sign is an additional infestation of ants because they love to feed on the honeydew.

Black sooty mould which grows in honeydew which aphids excrete
Black sooty mould grows in honeydew which aphids excrete

If you also come across a black, sooty substance on the leaves and stems, that’s a fungal disease that grows on the honeydew. While aphids are not the only insects to leave this secretion behind (many insects do), it’s a good bet that they are the cause if you haven’t got scale insects which are easy to identify, or wisteria scale if you have a wisteria.

What to do about these pests?


Sparrow feeding on aphids
Encouraging birds in your garden is a great way to control aphids

While you’re bothered by the aphids, they’re bothered by many other garden creatures (insects and birds etc) which treat them as food as already. Ladybirds, in particular, are their natural enemies, so having a naturally balanced ecosystem in your garden helps.

This means if you encourage these into your garden, (this could mean adding bird feeders to encourage birds or planting plants that are beneficial to ladybirds) this is a good way to keep the aphid numbers lower. Now my wife feeds the birds in our garden and I have noticed a big drop in the number of aphids. Wasps also eat a lot of aphids so instead of using wasp traps, perhaps leave them alone and let them do their part by eating the aphids.

Some plants are thought to deter aphids

Finally, you could try planting plants that are known to deter aphids. This is a trial and error, I’ve never seen amazing success doing this, but it could help. Sage, onions and garlic are great choices, and as a bonus, they are also great for cooking. When it comes to attracting birds, try planting shrubs and climbing plants that will provide homes for them.

Treatment for aphids

Blackfly aphids
Blackfly aphids

Organic methods to getting rid of aphids

The methods to get rid of aphids on plants range from manual removing them through to organic sprayers and chemical pesticides.

Manually, you can pinch off groups of aphids with your fingers and thumbs. Also, remove the leaves they’re snacking on. This method is ideal for smaller infestations, but it’s a useful way to keep on top of them early enough without needing to switch to chemicals. Doing this before infestations get out of control has proved to reduce aphid populations. I know some people rinse them off with streams of water from a hosepipe. Personally, I find this to be a waste of time.

Organic sprayers for aphids

If manually removing them is not effective enough or you have a large infestation, I would switch to natural organic sprays, for example, various plant/horticultural oils or pyrethrum. These oils (which can be purchased from most garden centres or online) have a short working life so you do need to reapply them. These can be used as a contact spray. The spray actually clogs up the pores that the aphids use to break. The problem with this is that it is a contact killer, you can kill the flies you spray directly, but new flies could be replaced within a day or two. What I will say is, this is also a good option as you can at least try and avoid spraying other plants.

Controlling large infestations with pesticides

Spraying aphids with pesticides id ideal for larger infestations
Spraying aphids with pesticides is ideal for larger infestations

If all this doesn’t work, move to a pesticide, I use these more than I perhaps should. I’ve tried getting away from pesticides, but they do such a good job. A lot of them are also systemic which means the spray is taken up by the plant into its system and it will continue to be effective for as long as 12 months.

Provanto Sprayday Greenfly Killer or Westland Resolva Bug Killer should do the trick, but there are many more available.

Deal with rust, mildew and black spot at the same time

But use them carefully as they’re not selective in the bugs that they kill if you have plants that are also suspectable to rust, mildew or blackspot, for example, roses or cornflowers. I would go for a double-action pesticide such as RoseClear. This will control both pests and diseases such as mildew, blackspot and rust.

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