Indiana’s state tree is a mess.
Homeowners with tulip poplar trees are finding and reporting that they are “raining” a mysterious film on their cars, homes and landscape plants.
The culprit—the tulip tree scale insect—is tiny, thirsty and sticky. The bug attaches to twigs and sucks the trees’ sap, leaving a sticky wake.
Tulip poplar, also called yellow poplar, was declared the state tree of Indiana in 1931. The tree is well-regarded and widely planted because of its beautiful flowers, form, the shade it provides, and rapid growth.
The tree’s sap is its life blood, carrying vital nutrients. The insect’s meals stress the tree and lead to its decline and, if untreated, potential death. Although tulip trees tend to be the scale’s favorite, the bug can also be found on basswood, persimmon, magnolia, catalpa, redbud and walnut trees.
“Depending on the condition of the tree today and any other stressors that may occur, the scale can result in the death of the tree, which may occur this year or in the future,” said Phil Marshall, director of the DNR Division of Entomology & Plant Pathology. “If the scale continues at heavy levels on the tree in 2013, the chance of tree death increases.
“Homeowners need to consider the hazard that tree creates to their property and decide if they should treat the tree or remove and replace it.”
The bug is a particular problem this year because the warm winter allowed a greater number of scales to survive, particularly in the southern part of the state.
As the bug feeds, it excretes a sticky waste product called “honeydew.” Honeydew is eaten by other insects, as well as by a fungus called sooty mold, which grows on the honeydew. The fungus often gives vegetation under infested trees a black moldy appearance, but is primarily an aesthetic problem.
Marshall said certain insecticide treatments can help control the scale, but if improperly applied can cause problems with other insects.
Right now, it may be too late treat with a soil-applied systemic insecticide, which takes two-to-three weeks before it moves up to the feeding site of the scale. Such treatment tends to be more effective in the fall or next spring, Marshall said.
“Tulip tree scale is in the crawler stage in late July and August and is most susceptible to a foliage-applied systemic insecticide at that time” Marshall said. “This treatment would need to be done by an arborist who has the equipment and knowledge to spray to the top of the tree.”
The cost for such treatment could range from a few hundred dollars to $1,000 per tree, based on size and difficulty of reaching the proper area with a spray.
“Another option to manage the scale is applying horticultural oil in the spring to smother the sedentary insects,” Marshall said.
During summer, the leaves, twigs and branches of affected trees will turn black from the growth of the sooty mold.
“Although it will cover the leaf and look bad, there is no need to take any action,” Marshall said. “By the time this happens, the tree has done most of its growing so the black color adds limited stress to the tree.
For more information call the Indiana DNR toll-free at 1-866-NO EXOTIC (1-866-663-9684) or their Purdue County Extension office at 1-888-EXT-INFO (1-888-398-4636) from 8:30 to 4:30 p.m. EDT.