Aphids are tiny, soft-bodied insects that are among the most common and successful pests in gardens, farms, and landscapes worldwide. Often no larger than a pinhead, they are often called “plant lice” due to their habit of forming dense colonies on new plant growth. Their bodies are typically pear-shaped, and they come in a surprising array of colors, including green, black, yellow, pink, and even a waxy white. While some species have wings, many are wingless, and they are known for their remarkably rapid reproductive rates.
These insects are dedicated herbivores, using their needle-like mouthparts to pierce plant stems and leaves and suck out the nutrient-rich sap. This feeding method is the primary source of the damage they cause. By draining a plant’s vital fluids, they weaken it, leading to symptoms like yellowing leaves, stunted growth, and distorted, curled foliage. A severe infestation can severely compromise a plant’s health and even kill it, especially young seedlings.
Perhaps the most noticeable and unpleasant side effect of an aphid infestation is honeydew. This is a sticky, sugary liquid that the aphids excrete in large quantities as they process the vast amounts of sap they consume. This honeydew coats leaves and surfaces below, creating a perfect medium for the growth of a black, sooty mold fungus. Furthermore, this sweet substance attracts other insects, particularly ants, which will often “farm” the aphids, protecting them from predators in exchange for the honeydew.
Despite their pest status, aphids play a significant role in the ecosystem as a key food source for many beneficial insects. They are a vital part of the diet for ladybugs, lacewings, hoverfly larvae, and parasitic wasps. This relationship makes them an important link in the food web. However, their ability to act as vectors for plant diseases is a major economic concern, as they can transmit harmful viruses from one plant to another with astonishing efficiency as they feed.
Species of Aphids
Green Peach Aphid
This is one of the most destructive and widespread aphid species. It is pale yellow-green in color and has a remarkably broad diet, known as being highly polyphagous. It feeds on hundreds of host plants, including peaches, potatoes, tomatoes, lettuce, and many ornamental plants. It is a major vector for over 100 plant viruses, causing damage far beyond the direct harm from its feeding.
Black Bean Aphid
As the name suggests, these aphids are a distinctive dull black color and often form very dense, conspicuous colonies. They are a serious pest of agricultural crops, particularly broad beans, sugar beets, and various ornamental plants like nasturtiums and viburnum. Their large, black clusters are easily spotted on the stems and undersides of leaves.
Woolly Apple Aphid
This aphid is easily identified by the white, cotton-like, or woolly wax filaments that cover its body. It feeds primarily on apple and pear trees, as well as on their roots and on American elm. The above-ground feeding can cause twisted, galled branches, while root feeding can stunt tree growth and overall health, making it a persistent problem in orchards.
Rosy Apple Aphid
A significant pest specifically for apple orchards, this aphid has a pinkish or purplish body covered with a light waxy powder. Its feeding causes severe curling and distortion of apple leaves and can stunt the growth of the fruit. After its initial cycle on apple trees, it migrates to narrow-leafed plantains for the summer, returning to apples in the fall.
Cabbage Aphid
This species forms dense, bluish-gray colonies covered in a light waxy coating on plants in the brassica family. You will find them clustering on the leaves of cabbage, broccoli, cauliflower, and Brussels sprouts. They are particularly troublesome because they can become embedded within the tightly packed leaves of the developing vegetable, making them difficult to control.
Melon Aphid
Also known as the Cotton Aphid, this species can vary widely in color from pale yellow to a very dark green, almost black. It is a major pest of agricultural fields and greenhouses, attacking a wide range of plants including cucurbits (melons, cucumbers, squash), cotton, and peppers. Its feeding can transmit viruses like Cucumber Mosaic Virus.
Pea Aphid
A large, light-green aphid that is a common and serious pest of legume crops. It primarily feeds on peas, alfalfa, and clover. While it can cause direct damage through feeding, it is also a proficient vector of several plant viruses that can devastate entire fields. Its size and color make it quite visible on plants.
Oleander Aphid
This bright, warning-colored aphid is a striking yellow with black legs, cornicles, and antennae. It is almost exclusively found on oleander, milkweed, and a few related plants. Its vibrant color signals to predators that it has ingested toxic cardiac glycosides from its host plants, making it an unpleasant and potentially dangerous meal.
Giant Willow Aphid
True to its name, this is a very large aphid, significantly bigger than most common species. It is a dark brown or black color and is typically found in large colonies on the stems of willow trees. Unlike many aphids, it remains active throughout the year, even in winter, and can be spotted on willow trunks on surprisingly cold days.
Spotted Alfalfa Aphid
This small, pale yellow or green aphid is identified by a series of four to six dark green spots running down its back. It is a major pest of alfalfa, causing “alfalfa yellows” from its toxic saliva, which stunts plant growth and can kill seedlings. It thrives in warm, dry conditions and can rapidly build up to damaging population levels in fields.
Corn Leaf Aphid
This aphid is a bluish-green color and often has dark-colored legs and cornicles. As its name suggests, it is a common pest of corn, sorghum, and other small grains. Large colonies can be found feeding deep within the whorl of the plant or on the tassels, which can interfere with pollination and cause direct damage to the developing crop.
Greenbug Aphid
Despite its name, this aphid is typically pale lime green with a darker green stripe down its back. It is a notorious pest of small grains like wheat, barley, and oats, and also attacks sorghum. Its saliva is toxic to plants, causing yellow to orange discoloration and necrotic spots on the leaves where it feeds, leading to significant yield loss.
Foxglove Aphid
This is a large, stocky aphid that ranges in color from light green to yellow. It has a preference for the buds and young leaves of a wide variety of plants, including potatoes, lettuce, and many ornamental flowers. Its feeding often causes severe leaf curling and distortion, and it is also an efficient vector for several plant viruses.
Bird Cherry-Oat Aphid
A common and economically significant aphid, it is dark olive-green to nearly black and is easily identified by a rusty red-orange patch at the base of its cornicles. It uses bird cherry trees as its primary winter host before migrating to a wide range of summer hosts, including oats, barley, wheat, and other grasses, where it can transmit damaging yellow dwarf viruses.
Potato Aphid
This is one of the larger aphid species and comes in two common color forms: pink and green. It has a long, slender body and long legs and antennae. It feeds on a wide array of host plants, including its namesake potato, as well as tomatoes, spinach, and beets. It is a key vector for potato leafroll and potato virus Y.
Rose Aphid
This is the most common aphid found infesting rose bushes. It can be either pink or green and often forms large, dense colonies on the tender new growth, flower buds, and stems of roses. Their feeding causes leaf curling, stunts the development of beautiful blooms, and produces large amounts of sticky honeydew that coats the plant.
Tulip Bulb Aphid
Unlike many aphids that feed on leaves and stems, this species is found underground or at the base of plants. It is a waxy, bluish-gray color and infests the bulbs of tulips, lilies, gladiolus, and other ornamental flowers, both in the field and in storage. Infested bulbs become weakened and can be prone to rot.
Woolly Elm Aphid
This aphid creates a striking visual on its host plant. It produces large, fluffy, white wax that completely covers its colonies, making infested branches look like they are covered in snow or cotton candy. It alternates between American elm trees, where it causes leaf galls, and the roots of apple and pear trees.
Lettuce Root Aphid
This pale yellow or whitish aphid is a specialist pest that lives underground. It colonizes the roots of its host plants, particularly lettuce, but also endive and chicory. The aphids are often covered in a white, waxy powder. An infestation can be devastating, causing plants to wilt, turn yellow, and become severely stunted, often leading to complete crop loss. They are particularly problematic in light, sandy soils.
Mealy Plum Aphid
This aphid is a pale green to yellow color and is covered in a faint, whitish, powdery wax that gives it a “mealy” appearance. It is a significant pest of plum and other stone fruit trees in the spring. Its feeding causes severe curling and crumpling of the leaves, which can stunt the growth of young trees. Later in the season, it migrates to various reed grasses before returning to plum trees in the autumn to lay its eggs.
Black Citrus Aphid
This shiny, dark brown to black aphid is a common sight on new, tender growth. It specifically targets citrus trees, forming colonies on young shoots, buds, and the undersides of leaves. While a heavy infestation can cause some leaf curling, its primary significance is as a vector for the destructive Citrus Tristeza Virus, which can kill trees grafted on certain susceptible rootstocks.