Tulip tree scale. Photo courtesy Purdue University
In the last several day, a great number of homeowners have been calling Indiana Department of Natural Resources office, including the state entomologist and forestry about the ‘rain’ dropping from the tulip trees (Liriodendron tulipifera) covering their cars, landscape plants and sidewalks.
This is honey dew, which is sugar water or the sap of the Indiana state tree that is sucked out of the twigs by the tulip tree scale, says Philip Marshall, state entomologist and forestry health specialist. The honey dew is passed through the scale’s body and excreted. The substance coats the upper leaf surface, grass and other plant leaves under the tulip tree creating a shiny or glistening appearance. The honey dew is sticky and hard to wash off your car once it hardens.
Tulip tree scale is native to Indiana and elsewhere in the United States, he says. “This epidemic occurs across most of the state and is likely to occur in other states of the Ohio River Valley. I have reports from Tippecanoe County in northern Indiana and from Indianapolis south to the Ohio River in the central and western part of the state I have not had reports from southeast, but it likely to be present.”
Tulip tree scale damage occurs primarily to saplings and young trees under 25 to 30 feet and 4 to 6 inch diameter in landscapes and street plantings. “In these situations, it is usually one tree or a few trees that are heavily infested and dying from the scale feeding and other stress factors. These trees have few leaves that are smaller than normal and the bark of the tree is black in color from the sooty mold.”
This year the scale is epidemic on tall trees — sawtimber size trees — as well as smaller trees in the forests and yards, Marshall says. “Since I’ve been around for a number of years observing the forest health problems across the state, unfortunately I have to say, this is the first time tulip tree scale has been at epidemic levels over a large areas of the state. I have never this happen before.”
Why is this happening now? Tulip tree scale is always present to some degree on a tree or a few trees in the forest. With the exceptionally mild winter, the scale population was not killed by low temperatures. The early spring that started in mid-March instead of mid- to late April, woke-up the scale and the trees and got the current situation started.
The raining of sap will continue into June and should decrease; although, some occurrence in the heat of July and August. The leaves and branches of the trees will turn black instead of the usually tulip tree gray bark as the sooty mold develops. The tops of the trees, besides looking black, will appear sparse because the leaves will be smaller and less dense. Over the summer and into next year, twig dieback will likely occur making the individual tree look bad.
“Another concern is summer drought and heat. Tulip tree is a drought sensitive tree and usually an indicator of a severe drop when the inner leaves starts to turn yellow and drop in July and August. If a drought occurs this summer, this will add to the stress already created by the scale and will lead to more decline and death of the trees in the forest,” Marshall says.
Everyone wants to know what to do to stop the messy dripping. They also want to know if their tree will die. Insecticide treatment is available but is only economical for yard trees not the forest.