Fighting aphids: How to get rid of them effectively and sustainably

Last updated on October 23rd, 2023 at 08:16 pm

Probably the best known lice are also the least problematic. Although they usually appear in large groups, they are very easy to see and can be easily removed. The small animals are usually green or black and have a proboscis with which they suck the plant sap from leaves and stems. We show you how to fight aphids.

We have probably all had the pleasure of encountering aphids (Aphidoidea). No wonder: The crawlers are found both in the garden and indoors on houseplants and spurn almost nothing that grows. The various species have specialized on certain plants. In Europe alone, for example, there are over 700 species of aphid! But don’t worry, not all of them are harmful to our plants. They also play an important role in the ecosystem, as they are a food source for many other insects and birds.

Of course, they can also cause damage, especially when they appear en masse. The good news is that aphids are easy to remove and gentle on plants. If you want to fight aphids, you have the choice between many different effective home remedies and can do without chemical pesticides.

Aphids: appearance and way of life

Aphids are very small and like to travel in large groups. Their appearance can vary: There are green, black, and brown aphids, as well as winged and flightless.

Green aphids are well camouflaged and are often not noticed until you look very closely. They sit densely packed on stems, stalks or shoots, making these areas look thicker. But they also like to settle in large numbers on the undersides of leaves. Dark aphids are noticed more quickly.

They all have proboscises with which they suck the plant sap from the leaves and shoots.

The aphid year begins in the spring. Depending on the temperature in winter, eggs, larvae or even adult females have survived. Only females hatch from eggs in early spring, but this is not a problem for reproduction. The aphid females can simply produce aphid babies without sexual reproduction – they clone themselves in the process. This is practical, because finding a mate would take a lot of time, and aphids are a popular food source for all kinds of other insects. So the key is to build up a large aphid colony as quickly as possible.

Aphids are quite clever: If it gets too crowded in one place or if the aphids are stressed by predators, the next generation is simply equipped with wings to colonize new plants.

In the fall, such winged specimens colonize other host plants. Male aphids are then also sired there. Their only task is to mate before winter so that the females can lay eggs that will survive the winter on the plants or in the soil. This ensures genetic diversity.

How to recognize an infestation with aphids: Damage pattern

Unfortunately, damage to plants usually only occurs when the infestation has already progressed. If the aphids sit on the undersides of the leaves, the leaves will eventually curl up as they dry out. These deformations are especially noticeable on very young, fresh leaves, because the leaves look downright curled.

Another type of damage that can occur with aphid infestation is bright spots or discoloration on the leaves.

On some plants, damage from aphids is limited. For example, lettuce is often infested. However, the leaves are delicate and sensitive, so control is difficult. With lettuce, after all, the whole plant is eaten, so we do not want to spray it with a pesticide. When the lettuce is already larger, it therefore makes sense to simply harvest it and wash the leaves thoroughly, instead of trying to combat the many small aphids already in the bed.

Don’t worry if an aphid did manage to hide on the lettuce leaf: Aphids are not poisonous and completely harmless to us humans.

 
Honeydew: The trail of the pests

Often, the aphid’s remains also reveal the presence of an infestation. The aphids digest the plant sap and excrete the undigested sugar it contains. This results in the formation of sticky layers on the leaves: Honeydew. If you have the impression that someone has dripped honey on your plant, then you can assume that aphids, scale insects or mealybugs have taken up residence on it.

The honeydew itself is not harmful to the plant. However, the layer can “clog” the leaves, making cellular respiration more difficult. The plant then cannot evaporate water and photosynthesize as well. The sugary honeydew is also an ideal breeding ground for fungi, for example the black sooty mold. It also attracts ants. They go crazy for the sweet stuff and therefore even defend the aphids against natural predators such as the ladybug.

So on plants with sturdy leaves, you should try to carefully wipe off the honeydew. Usually this works very well with lukewarm water. If the sticky film is more stubborn, you can dissolve some curd or soft soap in the water.
Which plants are infested by aphids?
Aphids on houseplants

The eggs of aphids can also survive in the soil and sometimes move in unnoticed when you buy a new houseplant. While this is annoying at first, it’s nothing to worry about. If you react quickly, the aphids will not spread any further.

Aphids are particularly fond of houseplants such as the rubber tree and other Ficus species, orchids, basket marants (Calathea) or dieffenbachias.

The same tips apply for controlling aphids on houseplants as for garden plants. You’ll find them later in this article.

 
Aphids in the garden

Unfortunately, virtually all plants can be infested by aphids because there are so many different, specialized species. For example, several species like to colonize apple and other fruit trees, the cucumber aphid can be found on cucumbers and pumpkins, the bean aphid loves legumes… There are aphids that specialize on currants, others on plums and damsons, still others on certain flowers. A real aphid classic in the ornamental garden are roses. Aphids often sit in heaps below the flower buds.

Getting rid of aphids quickly is especially important in the orchard to prevent damage to flowers and fruit set. Otherwise, the harvest may fail.

By the way, a real aphid magnet is the nasturtium. Especially black aphids gather under the large leaves. Nasturtiums are therefore often planted in the vegetable patch, as they distract the aphids from the other vegetable plants.
Fighting aphids: water march

For aphids, it is very effective to simply rinse them off the plants. They don’t stick too tightly to the leaves and are happy to just drop when stressed. Depending on the season and the infested plant, you have different options.

Smaller potted plants can be rinsed off indoors in the shower or in a larger sink. You can wrap the pot with the soil tightly in a plastic bag beforehand to keep it from getting all full.

Many spray bottles have so much pressure that you can easily remove aphids from your plants.

If you have a garden hose at your disposal, spraying larger fruit bushes or trees is particularly easy. Make sure there is sufficient distance to other plants, because the water splashes in all directions when it hits the leaves – and takes the aphids with it.

Fighting aphids: home remedies

Use home remedies in the fight against pests is always a good idea. They are gentle on plants, cheap and quickly made. Plus, you usually already have many ingredients in the house.

For liquid remedies for spraying, put old newspapers or something similar under the plant. The liquid will drip from the leaves and, depending on the ingredients, may leave stains on floors or carpets.

 
Plant-based home remedies

Many plants can be used to make extracts that help control aphids. Usually, the plants are boiled for this purpose or steeped in cold water for some time. With the decoction, the aphid-infested plants are thoroughly sprayed.

The quantities are not set in stone. Nothing will happen to your plants if you do not follow the grams or liters exactly. They are rather values for orientation.

 
Fighting aphids with wild plants

You can make a good home remedy against aphids from nettles, field horsetail or tansy, for example. These plants often grow wild on fallow land or along roadsides.

• Use a handful of fresh nettle leaves or dried nettles in a liter of cold water. Let the mixture steep for 1 – 2 days and spray the plant with it. You can also use the leftover brew diluted for watering.
• Use 100 – 150 g of finely chopped field horsetail per liter of water. Boil the plants for about 30 minutes. Let the decoction cool before using it. Alternatively, you can steep the mixture in cold water for a day. Then dilute it with water in a ratio of 1:5.
• For example: use 20-30 g of field horsetail in 200 ml of water; later dilute with a liter of water.
• Tansy can also simmer in water first: use about 50 – 100 g of the yellow flowers for one liter of water. Alternatively, tansy infuses in cold water for about a day. Then dilute the decoction with water in a ratio of 1:10.
• For example, use 10 – 20 g of flowers to 200 ml of water; later dilute with two liters of water.

 
Fighting aphids with oregano

You can also make such a decoction from oregano. It contains many substances that help to fight aphids. However, this is a bit expensive, because you need quite a lot of dried oregano for one batch. A good alternative is to have an oregano plant in your garden. You can cut it back regularly and dry it. You can also make the decoction from fresh oregano. Pour 10 g of dried oregano or 100 g of fresh oregano in a large cup of boiling water. After half an hour, pour the “tea” through a sieve and let it cool. Then dilute it with water in a ratio of 1:3 (for example, 200 ml of oregano decoction plus 600 ml of water).

If you have made too much spray broth, you can dilute it even further and simply water your plants with it. They have a strengthening effect and prevent pest infestation.

Fighting aphids: soap-based home remedies.

For the control of aphids can also use soap. However, no fragrant bars of soap or brightly colored shower gel, but curd or soft soap. These are available in any drugstore. Use 50 g of soap per liter of water. The water must be warm for the soap to dissolve. For solid curd soap, it works well to finely grate it so it dissolves faster.

Once the mixture has cooled, get to work on the aphids: spray the entire plant thoroughly with it and repeat the application after a few days.

If your plant is a houseplant with very fine foliage, you can also try the mixture on a small area first. Plants with somewhat thicker leaves, however, are usually not harmed by the soap.

 
Fighting aphids: oil-based home remedies

Mixtures for spraying that contain oil work well against aphids. The crawlers suffocate under the layer of oil or become immobilized. Some oils also contain ingredients that are toxic to the aphids – but completely harmless to us.

The oil is mixed with water. Since oil and water do not combine on their own, you need an emulsifier. You can use 1 – 2 squirts of washing-up liquid per liter of water. However, it should be an ecological product without dyes or fragrances.

The application should always be done in the evening or in the shade, so that the leaves are not damaged. If the leaves are still very oily some time after treatment, you can wipe them with a paper towel or similar.

 
Neem oil against aphids

Neem or neem oil is an oil extracted from the fruit of the neem tree. This tree grows mainly in India. Unfortunately, the oil itself is quite smelly, but it is extremely effective against many pests, as it prevents their larvae from developing further.

Neem oil dissolved in water is particularly good for controlling aphids. With neem oil, the vegetable emulsifier rimulgan is often recommended, but other emulsifiers can just as easily be used.

You can also buy ready-made mixtures with neem oil, but it is much cheaper to mix them yourself. You need only a little neem oil per liter of water, a teaspoon (just under 5 ml) is enough.

 
Rapeseed oil against aphids

Canola oil can also be used to combat aphids. In addition, the oil damages their eggs and larvae.

The specifications for a good canola oil mixture vary. They range from 10% canola oil and 90% water to 30% oil and 70% water. The younger and more sensitive your plant is, the less oil your mixture should contain. Some houseplants have very thin leaves and lettuce is also very delicate. More robust plants like most vegetable plants or fruit bushes and trees can also tolerate more oil. However, we recommend using less oil at first and adjusting the mixture as needed.

Caution, not all plants like canola oil: it is best to test the mixture on a small area first.

 
Other home remedies against aphids

There are quite a few other home remedies to combat aphids. Depending on what you have at home, you can try different tips. For example, black tea is said to help against aphids: Brew two bags of tea per liter of water and let it steep for a long time. When the tea is cold, you can spray it on your plants.

Garlic also has a deterrent effect on aphids. We don’t recommend just sticking garlic cloves in the soil, because aphids just multiply so quickly and the oils in garlic aren’t released fast enough that way. Instead, you can boil about 10 grams of minced garlic (or even onions) per liter of water, let it steep for a few hours, and strain the whole thing. Use the mixture undiluted and spray your plants with it often. However, this application is recommended mainly outdoors because of the smell.

 
How to fight aphids with milk?

Milk is popular as a home remedy because aphids cannot tolerate the lactic acid it contains. However, we recommend that you try other remedies first. Milk quickly goes bad at a certain temperature and starts to smell unpleasant. This may not be a problem outside, but the smell may attract flies, which is also not so pleasant.

Control aphids with beneficial insects

In summer, it’s a good idea to make your garden or balcony attractive to beneficial insects like the ladybug. Both the adult beetles and their larvae love to eat aphids. And they are not alone: lacewings and especially their larvae also eat aphids. Lacewing larvae are therefore also known as aphid lions.

Earwigs (earwigs), hoverflies, predatory bugs, spiders or garden birds – they all eat aphids. You can provide these animals with suitable shelter and other treats to make them feel at home and help control pests.

Insect hotels, for example, come in many different sizes and are fun to build yourself. Even a clay pot or old tin stuffed with straw makes a popular hiding place for earwigs and lacewings.

Nesting boxes can be installed in fruit trees. Little tits in particular like to feed on aphids.

You may have heard of buying beneficial insect larvae. However, we rather do not recommend buying larvae, because they usually can develop only under very good conditions. They have high demands on the right temperature and humidity. Only with luck the conditions at your home fit – otherwise the larvae do not hatch or die quickly.

Preventing aphids: the right planting.

Not only the animal beneficial insects can help when you need to control aphids, but also many plants. A mixed culture of vegetables, fruits, herbs and flowers is a great thing.

Most herbs contain essential oils. That’s what makes them so aromatic to us. Aphids, on the other hand, tend to be put off by the scent. Therefore, plant oregano, rosemary or thyme, for example, in the vegetable patch. On the balcony or terrace, you can place the herbs in pots close to vegetable or fruit plants.

Lavender and sage also have a deterrent effect on aphids, so they are often used for underplanting roses.

Some typical mixed culture partners in the garden are:

• Beans next to savory: Savory is effective against the black bean aphid and also enhances many bean dishes.
• Lettuce and cabbage next to chervil: The spice plant not only keeps aphids away, but also the cabbage white butterfly, whose caterpillars can cause great damage.
• Garlic next to strawberries: The oniony smell protects the sweet berries from aphids, and garlic is also said to prevent fungal infestation.