Aphids are tiny, soft-bodied insects often referred to as plant lice. They use piercing-sucking mouthparts to feed on nutrient-rich plant sap, and their presence is common in gardens and agricultural settings. While nearly any plant can host an aphid, certain species are significantly more susceptible to heavy colonization and damage. Understanding the plant traits that attract these insects is the first step in managing their populations.
Understanding Plant Characteristics That Attract Aphids
Aphids feed exclusively on the phloem, the vascular tissue that transports sugars produced during photosynthesis. Phloem sap is rich in carbohydrates but low in the amino acids necessary for insect growth. To compensate for this diluted nutritional profile, aphids consume a large volume of sap, leading to the excretion of excess sugar water known as honeydew.
The insects are highly attracted to plant tissues where the amino acid concentration is naturally elevated. This often includes the tender, rapidly developing tissues of new growth, such as shoot tips, flower buds, and young leaves. The sap in these areas provides a more readily available source of nitrogen compounds required for their quick reproduction.
Plant health also plays a role in susceptibility, as plants receiving excessive nitrogen fertilization often produce lush, soft foliage with high nitrogen content. This rapid, succulent growth provides an easier target for the aphid’s mouthparts to penetrate. Furthermore, aphids have a symbiotic relationship with the bacterium Buchnera aphidicola, which helps them synthesize essential amino acids from the limited supply in the plant sap, allowing them to thrive on this otherwise unbalanced diet.
Highly Preferred Edible and Ornamental Host Plants
The most common aphid species in home gardens are generalist feeders that target a wide variety of plants, particularly those with tender foliage. Among edible crops, the brassica family (cabbage, broccoli, cauliflower, and kale) are highly preferred targets, often hosting the Cabbage aphid (Brevicoryne brassicae). Other vegetables like lettuce, tomatoes, peppers, and beans are frequently colonized by generalist species such as the Green peach aphid (Myzus persicae), which has a broad host range of over 500 plant species.
On ornamental plants, aphids frequently congregate on the tight, soft growth of flower buds and young stems. Roses are a classic target, especially for the Rose aphid (Macrosiphum rosae), which favors the developing buds and young leaves. Other susceptible ornamentals include hibiscus, chrysanthemums, tulips, and plants within the Asteraceae family, such as asters and sunflowers.
Weeds serve as reservoirs for aphid populations before they migrate to cultivated crops. Common garden weeds like mustard weeds and thistles host large numbers of aphids, providing a local source of infestation for nearby vegetables. The Green peach aphid is known to use weeds as a temporary host before moving onto commercial crops.
Host Specialization Among Different Aphid Species
While many garden aphids are generalists, a significant number of species exhibit host specialization, restricting their feeding to one or two closely related plant families. These specialized species have evolved to overcome the unique defensive compounds in their specific host plants. Approximately 10% of aphid species are host-alternating, spending one part of the year on a woody “primary” host for sexual reproduction and overwintering, and the remainder on an unrelated herbaceous “secondary” host.
A common example of a specialist is the Woolly apple aphid (Eriosoma lanigerum), which feeds exclusively on the bark and roots of apple trees, causing galls to form on the stems. This aphid is easily identified by the white, waxy, “woolly” filaments it secretes that cover its body. Another example of this life cycle is the Rosy apple aphid, which uses apple trees as its primary host and migrates to plantain (Plantago lanceolata) for its summer generations.
Plants That Naturally Deter Aphids
Some plants possess natural chemical defenses that actively deter or confuse aphids, making them useful for companion planting near susceptible crops. Many of these repellent plants achieve this effect by emitting strong volatile compounds that mask the scent of the host plants aphids are trying to locate.
The Allium family, including garlic and chives, is highly effective because it releases volatile sulfur compounds that overwhelm the aphid’s sensory system. Strongly scented herbs are also excellent deterrents; mint and catnip, for instance, emit intense aromas that aphids actively avoid. Studies show that rosemary releases volatile organic compounds, such as camphor, which have a repellent effect on species like the Green peach aphid.
Certain flowers also contribute to aphid management. Marigolds release a strong scent that helps to confuse the pests, making them less likely to settle on nearby plants like cabbage or roses. Nasturtiums are unique because, while they can act as a repellent, they also serve as a highly attractive “trap crop,” luring aphids away from more valuable plants, such as beans or tomatoes.