What Are These Flying Bugs Resembling Cotton Lint?

DR. RAUL T. VILLANUEVA

LEXINGTON, KENTUCKY

Current Situation

Two colleagues at the University of Kentucky’s Research and Education Center and the public were asking me for the identification of a flying bug that resembles a snowflake or cotton lint. These insects have been observed in many areas of western Kentucky and landing on tobacco leaves, many ornamental shrubs, on car surfaces, or flying while people were walking.  

Identification & Description

This insect can be any of the several species of woolly aphids: alder (Prociphilus tessellatus), apple (Eriosoma lanigerum), elm (E. americanum), or hackberry (Shivaphis celti) woolly aphids. The appearance of woolly aphids is given by a waxy secretion that covers the body, legs, antennae, and around wings (Figure 1A through 1D) that makes them resemble a cotton lint or snowflake. Aphids are sap feeders of many plant species and excrete a liquid sweet waste substance known as honeydew. Honeydew, in many cases, accumulates on leaves, where a fungus called sooty mold can grow, turning leaves and branches black. Feeding of aphids can cause twisted, curled, or yellowed leaves and/or poor growth.

Not all aphids produce this wax structure, but other insects, such as white flies and psyllids, are also covered by wax. Researchers that studied the woolly oak aphid (Stegophylla brevirostris) in Florida hypothesized that the possible roles of these secretions might be to avoid contamination with honeydew, provide some protection against natural enemies, act as water-proofing protection, and reduce the efficacy of insecticides.

Management

Beneficial insects such as ladybeetles, lace wings, and parasitoids may be able to control aphids without the application of insecticides. However, woolly aphids may be sporadic pests, and outbreaks can be produced and require intervention to reduce their numbers. In these cases, plants can be treated with horticultural oils or soaps, and if required, conventional insecticides may be used.  ∆

DR. RAUL T. VILLANUEVA: University of Kentucky