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Some types of aphids have wings, which are transparent, longer than their body, and held like a roof over their back. One of the most common types are green peach aphids, which are able to infest hundreds of plant species, producing up to 80 offspring in a few weeks, and appearing well before its natural enemies, this pest is one of the first on the scene and quickly becomes problematic on garden plants. Other aphids may be green, pink, yellowish, black, or powdery gray. Nymphs resemble adults but are smaller and wingless. Aphids feed on most fruit and vegetable plants, flowers, ornamentals, and shade trees.
(Whether you're starting your first garden or switching to organic, Rodale’s Basic Organic Gardening has all the answers and advice you need.)
The problem with aphids? Both adults and nymphs suck plant sap, which usually causes distorted leaves, buds, branch tips, and flowers. Severely infested leaves and flowers may drop. As they feed, aphids excrete a sweet, sticky honeydew onto the leaves below. This allows a sooty mold to grow, which, in addition to being ugly to look at, blocks light from leaves. Also, some aphids spread viruses as they feed. In short, you don't want them in your garden!
Related: 14 Insects You Actually Want To Have In Your Garden
The life cycle of an aphid
Aphids reproduce like there's no tomorrow. Female aphids can reproduce without mating, giving birth continuously to live nymphs. Nymphs mature in 1 to 2 weeks and start producing offspring themselves. When days become shorter in the fall, both males and females are born. They mate, and then females lay eggs on stems or in bark crevices. The eggs overwinter and hatch the following spring. In very mild climates and in greenhouses, aphids may reproduce year-round. This is particularly troubling in greenhouses, as they can appear seemingly out of nowhere.
Outdoors, winged aphids' (like green peach aphids) eggs hatch around the same time that peach buds swell, often as early as February. The newly hatched females produce 30 to 80 clones until they become too crowded or their host declines. Then they start producing winged females, which disperse to hundreds of suitable host plants. These winged aphids are truly nefarious. Moving from plant to plant, they leave a few clones at each stop. Given that clonal offspring are literally born pregnant, just one aphid is an infestation in the making. Furthermore, the winged adults transmit viruses as they move between hosts. Despite being very weak fliers, winged aphids can spread for miles when carried by the wind.
Related: 14 Natural Ways To Control Garden Pests
How to control aphids naturally
Though aphids have amazing reproductive and dispersive capabilities, they are luckily only ephemeral pests in organic gardens with good floral diversity. Green peach aphids are like candy to their natural enemies. They readily fall prey to parasitic wasps, lady beetles, predatory maggots, and lacewing larvae. Infestations can usually be controlled simply by waiting for beneficial insects to arrive, so don't worry too much about them. (Also check out How To Control Earwigs In Your Garden—And Keep Them From Getting In Your House.)
Besides natural parasites, here are five more simple ways to control aphids without chemicals:
1. Early in the season, they can be dislodged with a strong jet of water. Drench plants with strong sprays of water from a garden hose to kill aphids. A hard, driving rainstorm will have the same effect.
2. Keep your plants as healthy as possible, and spray dormant oil to control overwintering eggs on fruit trees. (Read more about horticultural oils here.)
3. Ants and aphids are usually interdependent. Ants herd and care for aphids in order to keep a much loved food in constant supply: the honeydew with aphids naturally secrete. Control ants that guard aphid colonies in trees from predators by placing sticky bands around the trunks.
4. Spray aphids with organic gardening approved OMRI-listed insecticidal soap, summer oil (on tolerant plants), and homemade garlic sprays.
5. Provide food for aphid predators by mixing small-flowered plants like mints or yarrow throughout your garden. Just avoid overfertilizing with nitrogen; the resulting lush, juicy shoots are aphid magnets.