Cottony Maple Scale: Atlanta Identification & Treatment Guide

What Is Cottony Maple Scale?

Cottony Maple Scale is a soft scale insect (Pulvinaria innumerabilis, also referenced as Neopulvinaria innumerabilis) that feeds on the sap of maples and many other shade trees. It is most easily recognized in late spring and early summer by the white, popcorn-like cottony egg sacs the females produce along twigs and small branches.

How to Recognize It

• White, cottony egg masses about a quarter to half an inch long stuck to the undersides of twigs and small branches.
• Sticky honeydew coating leaves, branches, sidewalks, cars, or anything beneath the tree.
• Black sooty mold growing on the honeydew, leaving leaves and bark with a dirty, gray to black film.
• Premature yellowing or thinning of leaves, especially in heavier infestations.
• Dieback of small twigs and branches when populations build up over multiple seasons.
• Increased wasp, ant, or fly activity around the tree, drawn in by the honeydew.

The cottony egg sacs are most visible from late May into June. Crawlers (the mobile young) hatch from mid-June through July and move to leaf undersides to feed, and honeydew and sooty mold typically become most noticeable in mid to late summer. The scale overwinters as immature nymphs on twigs and bark.

Why It Matters for Atlanta Trees

In most years, natural predators and parasitoids keep cottony maple scale at low, tolerable levels, but every few years populations can spike and cause heavy honeydew, sooty mold, leaf drop, and branch dieback. A tree already stressed by drought, poor soil, or construction damage can decline further or lose limbs, and dead branches over driveways, walkways, or homes can become a falling-limb hazard if the infestation is left unchecked. In Atlanta yards, the species most often affected include silver maple, red maple, sugar maple, boxelder, honeylocust, hackberry, white ash, dogwood, sycamore, elm, linden (basswood), and oak.

General Prevention

• Keep trees vigorous with deep, infrequent watering during Atlanta's summer dry spells rather than light, frequent watering.
• Maintain a 2 to 4 inch ring of mulch over the root zone, kept back from the trunk, to conserve moisture and reduce root stress.
• Prune out small infested twigs and dead branches during the dormant season to remove overwintering scales and reduce hazard limbs.
• Avoid broad-spectrum sprays that kill the lady beetles and parasitic wasps that normally keep scale populations in check.

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 try to scrub, pressure-wash, or scrape the cottony egg masses off the bark. It rarely reaches enough of the population to matter, can damage thin bark, and does nothing to address the crawlers that will emerge later in the season.

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: Ohio State University Extension (Ohioline), University of Wisconsin Horticulture Extension, The Morton Arboretum, and Penn State Extension.