If you’ve seen insects living on your plants and you aren’t sure what these insects are, you might have a very common backyard and indoor pest: aphids.
Aphids are small insects with soft bodies that live on plants and trees. They are about 1/16 to 1/8 inches (1.5 – 3 mm) long. Their heads are narrower than their abdomens, which gives them a pear shape. Aphids come in many colors, such as green, white, black, brown, yellow, gray, pink, or red.
With over 4 000 aphid species, it’s impossible to list every kind of aphid and what it looks like here. But there are certain things that all or most aphids have or do, which I share with you below. If you go through the following list, you will know exactly what to look for to identify if you have aphids on your plants or if it’s another insect.
Baby aphids look like small adult aphids
If you find aphids on your plants or trees, look for a mix of adult aphids and their babies, called nymphs. These nymphs look a lot like the adults, except they are smaller in size.
During spring and summer, you should see a lot more nymphs than adults. Aphids live for about one month, and each aphid can give birth to between 50 and 200 pregnant female nymphs in that month. Within one week of being born, pregnant nymphs start giving birth to their own pregnant nymphs.
When it’s warm, there is always a strong supply of nymphs being born to grow the colony.
Aphids can have wings or be wingless
Most aphids are wingless, but aphids are born with wings when they need them. If you see winged aphids, they will be a little darker in color and have longer antennae than the wingless aphids of the same colony.
Aphids are born with wings for one of two reasons:
- When the seasons change in springtime and in fall, winged aphids are born to fly away and start their own colonies on other plants or trees
- When a plant or tree with an existing aphid colony gets overcrowded and shows signs of damage or possible death, winged aphids are born so they can leave the colony and start a new colony on another healthy tree or plant
Aphids have long antennae
Aphids are insects. Insects don’t have noses like us – they use their antennae to smell the world around them.
Aphids use their long antennae to smell the chemicals on plants, so they know what type of plant it is and if it’s something the aphid wants to eat.
If you are working with plants with your bare hands, you might get the chemical smell of the plant on your hands. An aphid could try to bite you to taste you because it thinks you are that plant!
Aphids have two tubes on the end of their abdomen
Aphids have two short tubes, called cornicles, on either side at the end of their abdomen. These cornicles look like exhaust pipes and can be large and obvious or small and be difficult to see.
Aphids release chemicals and pheromones from these cornicles to communicate with other aphids, and other aphids smell these chemical messages using their antennae.
Aphids molt and leave white skins on plants
Aphids have a hard, non-living outer skeleton instead of skin. This outer skeleton, called an exoskeleton, does not grow with the aphid. When an aphid gets too big for its exoskeleton, it sheds the exoskeleton or molts, leaving behind a white skin called a cast.
Nymphs molt and leave behind skin casts four times in their lives as they grow into adults. If you see white flakes or old skins on your plants, you probably have aphids.
Some aphids have a woolly coating for protection
Woolly aphids are most often seen on trees and shrubs in fall.
They have a white, fluffy, stringy covering to protect themselves from predators, such as ladybugs, lacewings, and parasitic wasps. This wool-like protection makes the aphids look like they’re covered in mold, so predators don’t want to eat them.
The wool on woolly aphids isn’t actually wool or cotton, it is wax made by glands in the insect’s abdomen. If you see white, fluffy clusters on your trees and shrubs, you most likely have a colony of woolly aphids living there.
Aphids have pear-shaped bodies
Aphids are pear-shaped, which means that their heads and middle sections are narrower than their wider abdomens.
Their abdomens need to be wide for several important reasons. Aphids need to be able to carry and give birth to many live nymphs in their short lifetime. The abdomen is also where aphids release a sweet substance called honeydew when sucking the sap out of plants, and where the cornicles or tailpipes sit to release pheromones and communicate with other aphids.
Aphids usually live in large colonies
Source: With thanks to Roger Schmidt, University of Wisconsin-Madison, Bugwood.org
Though rare, you might see one or two aphids alone on a plant. These aphids will probably have wings, and they have just arrived to start a new colony.
Usually, you will find hundreds of aphids huddled close to each other on a plant or tree, usually under a leaf or on a plant’s soft new growth areas, such as a flower bud.
Ants are often seen near aphid colonies
Aphids release a sweet goo called honeydew from their anuses when they suck the sap out of plants. Honeydew is many ants’ favorite food, and so ants often farm aphids and take care of aphid colonies to eat their honeydew.
If you see what you think is a colony of aphids, look for ants nearby. These ants are there to protect the aphids from predators, carry aphids to new plants when this plant starts dying, and to suck the honeydew directly from the aphids and take the food back to their own nest.
Live aphids come out in warm weather
Aphids prefer warm climates, although they are found all over the world.
If aphids live in a place that gets cold, they overwinter. This means that they lay eggs that can survive very cold winters, and baby aphids hatch in springtime to start new aphid colonies.
You are more likely to find active aphid colonies all year round if you live in a sunny, warm place or if you have aphids on your indoor plants, where you keep the temperature fairly steady. But if there are cold seasons where you live, you may only find live aphids in spring and summer and aphid eggs in fall and winter.
Aphids are found on the softer parts of plants and trees
All aphids feed on the softer, tender, and juiciest parts of plants and trees. Aphids eat by piercing a plant with their mouthparts and sucking out the plant sap running inside. An aphid’s mouthparts cannot pierce any hard parts of plants and trees, such as wood or bark.
When looking for aphids, you will most commonly find them on the underside of leaves, on new shoots, on plant stems, and on flower buds. But not all aphids live and feed above ground – some live in the soil and eat your plant’s tender roots.
Aphids are found on most plants and trees
It’s possible to find aphids on pretty much any plant, crop, tree, or houseplant. This includes citrus trees, vegetables, milkwood, tomato plants, petunias, and roses.
Some aphids will attack many different types of plants, while other aphids will eat only one or two types of plants.
Aphids drop a sticky substance called honeydew
If you find insects on your plant that look like aphids, check the plant’s leaves and stem below the insect colony.
Aphids release a lot of honeydew when they suck sap from the plant, and this honeydew falls from the aphids to the leaves and branches below. If you find a sticky substance or black sooty mold growing on the plant, then you probably have aphids.
Best products to get rid of aphids
If your backyard or houseplants are plagued by aphids, here are the top recommended products from Amazon to get rid of these pesky insects:
Bonide Ready-to-Use Insecticidal Soap Spray: This is an option for indoor and outdoor plants, including houseplants, citrus, ornamentals, fruit trees, and vegetables. The spray must make contact with the aphids to kill them.
Bonide Rose Spray: Don’t let the name fool you – this spray isn’t just for roses. It kills all life stages of aphids on roses, flowers, potted plants, indoor plants, ornamentals, shrubs, fruits and vegetables, and more. It also kills sooty mold and prevents fungal attacks.
Houseplant Insect Control Granules: These granules can be used on houseplants, flowers and roses, but not on any edibles like fruits and vegetables. The granules are highly recommended for potted plants or plants in containers and raised beds.
Food-Grade diatomaceous earth: Sprinkle this all-natural, organic product on your aphid-infested plant and around the bottom of the plant or tree. When aphids walk over the diatomaceous earth, it cuts them and kills them, yet this is not harmful to humans. Be sure to use this earth when it is dry, and sprinkle more after it has rained.
