Aphids
Pest · Commonly affects: Tomatoes, Peppers, Lettuce and leafy greens, Cabbage and other brassicas, Beans, Squash and cucumbers
Aphids are small, soft-bodied, pear-shaped insects that feed by sucking sap from the tender growth of a wide range of garden plants. They matter to gardeners because they reproduce very quickly in warm weather, build up into large colonies within days, and can weaken plants and spread viral diseases.
How to identify it
Look for clusters of tiny insects, often less than one-eighth of an inch long, packed along stem tips, flower buds, and the undersides of leaves; they come in green, black, yellow, pink, gray, or white depending on the species. Two short tubes called cornicles project from the rear of the body, which helps separate aphids from other small pests. A giveaway sign is sticky, shiny honeydew on leaves and surfaces below, sometimes with black sooty mold growing on it and ants patrolling the colonies.
Damage
Their feeding drains plant sap, causing leaves to curl, pucker, yellow, and become distorted while shoots grow stunted and misshapen. The sticky honeydew they excrete fuels sooty mold that coats leaves and blocks light, and many aphid species transmit plant viruses as they move from plant to plant.
Prevention
Avoid overfeeding plants with high-nitrogen inputs, since the flush of soft new growth is exactly what aphids prefer; aim instead for steady, balanced fertility and healthy soil that produces sturdy plants. Space and prune plantings for good air movement, control ant activity that protects aphid colonies, and clean up weeds and crop debris that shelter overwintering aphids. Rotate annual crops between seasons and choose vigorous, locally adapted or resistant varieties where they are available.
How to manage it
A strong spray of water from a hose knocks aphids off leaves and stems, and small infestations can be wiped off or the worst-hit shoots pruned out and removed from the garden. Encourage and protect natural predators such as lady beetles, lacewings, hover fly larvae, and tiny parasitic wasps by growing flowering plants nearby and tolerating a few aphids so beneficials have something to eat. Floating row covers keep aphids off young or transplanted crops, and steady, even watering keeps plants from becoming stressed and overly attractive.
General guidance for US home gardens, focused on prevention and non-chemical control. For a confirmed diagnosis and options specific to your area, contact your local Cooperative Extension office. Page updated Aug 4, 2026.