A large number of inquires have been received in Indianapolis office as well as the forestry district forester offices from homeowners calling to find out about the ‘rain’ dropping from the tulip trees covering their cars, landscape plants and sidewalks.
This is ‘honey dew’ which is sugar water or the sap of the tulip tree that is sucked out of the tulip tree twigs by the tulip tree scale. It is passed through the scales body and excreted as ‘honey dew’. This 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 when it hardens.
Tulip tree scale is native to Indiana and the U.S. 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 IN and from Indianapolis south to the Ohio River in the central and western part of the state I have not had reports from south east IN, but it is likely to be present.
Tulip tree scale damage has been present in the past primarily to sapling and young trees under 25-30 feet and 4-6 inch diameter in yards and urban 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. 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 in the forests and is occurring over a large areas of the state.
Why is this happening now? Tulip tree scale is always present to some amount on a tree or a few trees in the forest. With mild winters and especially the lack of a ‘winter’ this past 2011/2012 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, but still occur, as the heat of July and August occurs. The leaves and branches of the trees will turn a black color instead of the usually gray color of tulip tree bark over the next weeks with the development of sooty mold. The tops of the trees, besides looking black in color, will have a sparse appearance as the foliage will be smaller and fewer from the impact of the feeding. 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.
What can you do to stop the ‘rain’? And will my tree die? Insecticide treatment is available but is only economical for yard trees not the forest trees. For large yard trees it would be advisable to use an arborist. Homeowners can apply the systemic insecticide imidacloprid as a soil drench at the base of the tree. However, it will take 2-3 weeks for the insecticide to move up through the tree.
For smaller trees homeowners can reach to the tree top with their sprayer, they can apply a systemic insecticide in late July or early August when the next generation of crawlers hatch out. Orthene is one systemic insecticide available for homeowner use. In March or April of 2013, the homeowner can apply a dormant oil that will suffocate the scale.
REMINDER- All users will need to read the label before they purchase the insecticide and to read it again before they use it. Imparitive to follow the label directions.
INDNR, http://www.in.gov.dnr, will be documenting the occurrence of this epidemic. Please contact Philip Marshall at my office number, 317-232-4189. We welcome all phone calls with any further questions.
Purdue Extension Publications to help – E-29 SCALE INSECTS ON SHADE TREES AND SHRUBS, http://extension.entm.purdue.edu/eseries3/view.php?article=articles/scale_insects_on_shade_trees_and_shrubs.txt&id=1§ion=Landscape.