Woolly aphids (subfamily: Eriosomatinae) are sap-sucking insects that produce a filamentous waxy white covering which resembles cotton or wool.

[citation needed] Woolly aphids feed by inserting their needle-like mouthparts into plant tissue to withdraw sap.

As a result of feeding on the sap, woolly aphids produce a sticky substance known as honeydew, which can lead to sooty mold on the plant.

[citation needed] Woolly aphids and other sucking insects are often vectors of transmission for powdery mildew (a white fungus which grows on above ground parts of some plants), and other infectious diseases.

Aphids penetrate plant surfaces where they often reside and provide a host of potential inoculants through physical, digestive or fecal secretions.