What are Aphids?

Niki Foster
Niki Foster

Aphids are tiny herbivorous insects in the superfamily Aphidoidea, within the order Hemiptera, which also includes cicadas, gnats, and many other "true bugs." There are ten families of aphids and about 4,000 species. They live around the world, but are most common in temperate areas. About 250 of the species are considered pests in forests and gardens.

Aphids feed on the sap of plants.
Aphids feed on the sap of plants.

Though aphids are only 1 to 10 millimeters (about 0.039 to 0.39 inches) long, they can present a huge problem to plant life. The insects feed on the sap of plants by piercing the phloem, the vessels through which sap flows, with a long proboscis. As they feed, they can introduce viruses to the plants, sometimes devastating ones. Even if they don't introduce disease, the bugs can destroy the appearance of plants simply by their feeding and breeding activity. Some feed only on a single plant species, while other types feed on hundreds of different plants.

Ladybugs eat aphids.
Ladybugs eat aphids.

Some of these insects have symbiotic relationships with other species. Some are "farmed" by ants, which protect the aphids and feed on the carbohydrate-rich honeydew they secrete. Others host Buchnera bacteria, which live in specialized cells inside the insects and synthesize amino acids that are not present in the aphids' diet.

Many species have very unusual reproductive methods. Typically, the insects mate in the autumn, and the fertilized female lays eggs. The eggs hatch in the spring, but only produce females, each of which may be winged or wingless.

The females born in the spring produce parthenogenically, without being fertilized. The daughters are therefore genetically identical to the mothers, and multiple generations may exist within an individual. Births at this point may be live, or the insects may lay eggs. In the fall, some develop into males, and the cycle begins again.

Through parthenogenesis, aphids are able to reproduce extremely quickly and in huge numbers. Those that live inside greenhouses or in areas with mild winters can continue to reproduce asexually for years. It is easy to see how they can become such a menace to their host plants.

Aphids are often kept under control by their natural predators, which may be introduced into a garden for that purpose. Aphid predators include ladybugs, lacewings, hoverfly larvae, parasitic wasps, and some parasitic fungi. These insects may also be controlled by spraying the plants down with plain or soapy water, pruning affected areas, and using aluminum foil mulch. Pesticide is also an option, though the least recommended.

The insects feed on the sap of plants by piercing the phloem, the vessels through which sap flows.
The insects feed on the sap of plants by piercing the phloem, the vessels through which sap flows.
Niki Foster
Niki Foster

In addition to her role as a wiseGEEK editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology.

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Discussion Comments


I have a balcony garden -- a very controlled environment. I do have aphids on my strawberry plants and on my peach tree. I use 'painters' tape to get rid of the visible aphids. I very gently only touch the tape to the aphids and get rid of them. --Snofyre


@Izzy78 - I lived in Florida for a couple of years, and they had what they called citrus aphids. They basically did the same thing and dropped sticky stuff all over the ground. Of course, in their case, they put on a lot of chemicals to kill them before they damaged the crop.

I live in the Midwest now, and I have a beech tree in my yard that I was recently told had a kind of aphid growing on it. I don't know if they are the same thing you were talking about or not, but these are small, cottony-looking bugs. They only show up on a few of the branches, but they completely cover the thing. Whenever the wind blows, they all start swaying, too. At first I didn't know what it was. I thought it was fungus or something. Then I looked closer and saw they were individual bugs.

I sent a letter to my state extension agent and she said they were beech aphids. They don't usually do any permanent damage to the tree, but told me of ways I could get rid of them if I wanted.


Where I live, we have something called tree aphids. I assume they are true aphids and not just something that people call aphids. I have never personally seen them, but I know I have had them before because they drop the honeydew stuff all over the yard.

It is impossible to park your car under a tree that has the aphids, or it will end up covered in a sticky mess. I am lucky that the tree they always show up on is in the corner of the backyard where I don't spend a lot of time.

Does anyone else have these aphids in their yard? Like I said, they aren't really a problem. They don't kill the tree or anything. They just cause a mess.


@TreeMan - I agree. It is always best to use the least force possible to get rid of aphids, but they can be tricky. I have not heard of planting garlic, but I have a friend who plants dill in her garden to prevent aphids. I think what those plants do is attract ladybird beetles and the other insects that feed on aphids.

Fortunately, I have never had a problem with aphids in my garden. What I do have, though, is Japanese beetles. What I have found works for them and a lot of other insects is just getting a spray bottle and filling it with water and some dish soap. If you spray that on the insects, it suffocates them somehow, and they eventually die off if you spray them every day. Like I said, I've never had a problem controlling aphids, so I don't know if it works on them, but it's a cheap, safe method to try.


@sputnik - Interesting, I didn't know that there were any plants that were able to keep aphids away. Do you have any idea how they work? Do they produce some chemical that kills the aphids when they eat it, or do the aphids just not like being around those plants?

I have a pretty large flowerbed, and I get aphids about every year. I also have a relative who owns a greenhouse, and aphids are a huge problem there if they are allowed to reproduce. Like the article says, using pesticides isn't as good as being able to use more natural remedies to kill aphids.

Unfortunately, I haven't found a good home remedy yet, so I have just been forced to use some type of aphid spray any time I find them.


The natural enemy of blackfly, or aphids are lady beetles, but they can also be kept under control but planting plants like garlic, or a nasturtium between the vegetables.

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