Across Indiana this week, homeowners with tulip poplar trees could be finding their cars and landscape plants covered in a mysterious sticky film.
This time of year, tulip poplars are easily recognized by their leaves, which resemble a tulip and the 2-inch long lime green and orange flowers in the canopy.
The culprit in the sticky mess could be the tulip tree scale insect, a small, sap-sucking bug that feeds on the trees' branches.
Declared as the state tree of Indiana in 1931, tulip poplars are well regarded and widely planted for their beautiful flowers and form, shade and rapid growth. The tree's sap carries vital nutrients, and feeding by the insect can cause damage to the trees in addition to the unsightly mess.
Though it is a native insect, the scale can reach high numbers on tulip and magnolia trees.
As the bugs feed on the branches, they excrete a sticky waste product called "honeydew," which rains down out of the infested tree canopy and onto objects below.
The honeydew is a favorite food of other insects such as ants and wasps, as well as a fungus called sooty mold.
Sooty mold growing on the honeydew often gives vegetation under infested tulip trees a black moldy appearance, but is primarily an aesthetic problem.
Heavy tulip tree scale infestations can cause yellowing and drop of leaves, branch death or whole tree mortality in smaller trees. Homeowners with tulip trees can recognize tulip tree scale on sticky trees by looking for mottled orange bumps about 3/8-inch long left by last year's female scales.
This year's scales are black and flattened and only about 1/8-inch long. They have yet to mate and plump up with this year's eggs.
Certain insecticide treatments can help control scale populations and their damage, but if improperly applied can kill bees and create other problems.
A soil-applied systemic insecticide such as imidacloprid, can provide control if applied now. It will take at least three weeks to get up into the tree canopy, by which time the flowers will have fallen off the trees, diminishing the impact on bees.
Although foliar sprays can be effective, most homeowners lack the equipment they need to reach the treetops.
These products are best applied by a tree care professional.
For more information on control options and some background on scale insect, call the local Purdue Extension Office at 448-9041 or call 1-888-EXT-INFO.