Woolly Aphid Identification Guide

Key Features

• Small, soft-bodied insect, typically only 1-2.5mm long individually, but almost always seen in dense clusters
• Body is covered in long, white to bluish-white waxy filaments that give the colony a cottony or "woolly" appearance
• Underneath the wax, the body itself is usually dark blue-gray, purplish, or blackish
• Clusters often look like patches of white fuzz or mildew on stems and branches before you look closely enough to see individual insects moving
• Winged forms, when present, have smoky-tinted wings and a less waxy covering than wingless nymphs
• When disturbed, the waxy coating can rub off, revealing the soft body underneath

Where and When to Look

• Found clustered on twigs, branches, trunks, and sometimes leaf undersides of host trees such as apple, elm, alder, and hawthorn, depending on the species
• Most noticeable from late spring through fall, when colonies build up on new growth and bark crevices
• Often found near pruning wounds, cracks, or areas of tender new growth
• Colonies can also appear on roots of some host plants, hidden below the soil line

Similar-Looking Bugs

• Mealybugs also have a white, waxy covering but tend to have a more segmented, mealy appearance rather than long cottony filaments, and are usually found on softer garden and houseplants
• Cottony cushion scale produces a similar white fluffy mass, but the wax forms a single large, fluted egg sac attached to an otherwise stationary insect rather than covering many small, mobile aphids
• Wax-covered whitefly nymphs are much smaller and flatter, without the long filamentous wax strands

Quick ID Checklist

• Dense clusters of tiny insects covered in white cottony wax
• Dark body visible when wax is rubbed away
• Found on twigs, bark crevices, and new growth of host trees
• Cottony patches that move or scatter when touched (unlike mold)
• Present spring through fall on branches and stems