Aphids: Atlanta Diagnosis & Treatment Guide

What Is Aphids?

Aphids (family Aphididae) are small, soft-bodied sucking insects that feed on plant sap from leaves, new shoots, and bark. Most species are about 1/8 to 1/4 inch long, range in color from green to yellow, brown, or black, and have a pair of small tube-like cornicles projecting from the rear of the abdomen. Atlanta hardwoods are also affected by larger species such as the giant bark aphid (Longistigma caryae).

How to Recognize It

• Sticky, shiny coating (honeydew) on leaves, branches, sidewalks, vehicles, or anything parked under the tree
• Black, sooty mold growing on leaves and bark where honeydew has accumulated
• Clusters of small insects on the undersides of leaves or on tender new growth
• Curled, distorted, yellowing, or stunted new leaves and shoots
• Heavy ant activity running up and down the trunk (ants tend aphids for their honeydew)
• Wilting or general loss of vigor on heavily infested limbs

Populations typically build in spring on tender new growth, often peak again in late summer and early fall (especially for the giant bark aphid on hardwoods), and decline in cold weather.

Why It Matters for Atlanta Trees

Most healthy, mature shade trees tolerate aphids without lasting harm, but heavy or repeated infestations can distort new growth, reduce vigor, and let sooty mold block sunlight on leaves so the tree photosynthesizes less. Honeydew and sooty mold also damage the appearance of cars, decks, patios, and plants growing under the tree, and stressed or young trees can decline if infestations are left unchecked. In Atlanta yards, the trees we most often see affected include hackberry, crapemyrtle, tulip poplar (yellow poplar), maple, oak, pecan and hickory, river birch, willow, sycamore, and pine.

General Prevention

• Avoid over-fertilizing, especially with high-nitrogen products, because flushes of soft new growth attract aphids
• Water trees deeply during drought and mulch properly to keep them vigorous and better able to tolerate feeding
• Inspect tender new growth weekly during the growing season so problems are caught while populations are small
• Protect beneficial insects (lady beetles, lacewings, parasitic wasps) that naturally keep aphid numbers down by avoiding broad-spectrum sprays in the landscape

What NOT to Do

• Do not self-diagnose. Many tree problems look alike, and treating the wrong one wastes time and can harm the tree.
• Do not apply fungicides, insecticides, or other chemicals without an arborist's specific recommendation. Wrong product or wrong timing makes things worse.
• Do not reach for a broad-spectrum spray at the first sign of honeydew. These products often kill the lady beetles, lacewings, and parasitic wasps that were already holding aphid populations down, and infestations frequently rebound worse than before.

Related Services

For most diagnosis and treatment questions, the right starting point is one of our services:

• ISA-Certified Arborist Services: diagnosis, consultation, second opinion
• Plant Health Care (PHC): ongoing tree health management
• TRAQ Tree Risk Assessment: when the tree may be a safety hazard

Sources

This page summarizes general information from: NC State Extension, UF/IFAS Extension, UGA Extension (Bartow County), and UGA Extension.