Mysterious Mount Prospect soot is actually from an insect called cottony maple scale
Residents in Mount Prospect have been wondering about a sticky black soot-like substance coating their outdoor surfaces. Turns out, it's actually secretions from a bug.
The stick residue has been popping up all over people's trees, cars and mailboxes. But the cause isn't a fire; it's an insect called cottony maple scale.
The soot-like residue is resilient; not even Wednesday's rain could wash it away. The substance left behind by the cottony maple scale is called honeydew. It then creates a black, sooty mold which is what people see.
Mount Prospect officials say the residue is a fairly common seasonal occurrence, but it's definitely more pronounced this year.
"We've actually been getting calls throughout the summer, going out and investigating in this area at this particular time," said Dave Hull, the forestry and ground superintendent of the Village of Mount Prospect Public Works Department. "This is something that we typically deal with every season. It has been higher than normal this year, for sure."
Hull said there's multiple factors that can lead to the high presence of the sooty mold this year.
"That increase is typical in an insect cycle. Right now they're cycling up, populations are high," he said.
Hull said other factors, like drought and mild winters, are a one-two punch of creating more stress for trees, which in turn prevents insects from dying off in typical umbers. That then leads to population blooms like the one being experienced right now.
"Mild winters over the past few years, that certainly is allowing a lot more insects, in my opinion … that typically would be killed off in a more harsh, cold winter."
Spencer Campbell, plant clinic manager at the Morton Arboretum, said while the black sooty mold can be a concerning sight, it's nothing too alarming.
"It doesn't typically result in any lasting damage. It's naturally occurring, and this will all be done here in just a few weeks when the leaves drop," he said. "Healthy trees are typically able to recover once that population starts to decline, once those natural predators start to meet the local population of the cottony maple scales."
Mount Prospect Public Works does treat affected trees that are on public property. If you have an affected tree on your own property, there are treatments available to help, like horticultural oils.