Last summer and fall, numerous residents living in Martha’s Vineyard and several coastal communities in Massachusetts were shocked and displeased to find a thick layer of sticky black soot covering vehicles, homes, patios, fences, sheds, trees, plants, grass and just about everything that can be found in residential areas. Last July, one resident of Sandwich, John Recker, found that his brand new white fence had inexplicably turned black overnight. After removing the mysterious black matter from his fence with bleach and a garden hose, the soot returned. A few days afterward, it also appeared on Recker’s patio, cars, lawn furniture, landscaping plants and house, and homes throughout his neighborhood had also been affected.

The origin of the sticky black soot became a matter of intense speculation within Recker’s neighborhood. Many residents believed that the soot had originated from jet exhaust from the nearby Barnstable Municipal Airport, but the soot was also found covering residential landscapes in Brewster, Bourne, Martha’s Vineyard and many other coastal areas. Complaints became common across eastern Massachusetts, and eventually, entomologists and pest control professionals in the state revealed the soot to be excrement left by an abundance of yard-dwelling scale insects.

Several arthropod pest species digest and excrete black honeydew after feeding on sap from trees and woody plants. These common yard pests are known as lecanium scale insects, and due to their unusually abundant population this year in eastern Massachusetts yards, their honeydew byproduct accumulated throughout residential neighborhoods in the area. Due to their tiny shell-like appearance, scale insects are hard to notice on trees and plants, even when they are unusually numerous.

While the feeding activity of scale insects rarely cause significant damage, trees, lawn grass, and garden plants that become covered in their honeydew excrement often die from lack of sunlight. The honeydew also damages house siding and cosmetic paint on cars, and damaging fungal growths usually emerge from the excrement. Perhaps worst of all, the honeydew’s sugar-rich content attracts numerous types of insect pests onto properties, including ants, roaches, flies, wasps and many others. Scale insects can also be transported indoors via infested houseplants, and the excrement can rain down on residential areas for months. Scale insects are very difficult to exterminate, and the accumulation of their sugary excrement cannot be halted.

Have you ever noticed the honeydew excrement on your property?