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Recent dry weather and a mild winter have created a perfect storm of tulip tree scales, small sap-sucking bugs that latch onto tree branches, leaving behind a sticky mess.
The aptly named bugs aren’t much to look at. About the size of a small pea, they could be mistaken for brownish scales or knots on tree branches.
“For some reason, this is the year,” said Clifford Sadof, an entomologist with Purdue University.
The sap-loving critters are wingless until adulthood, and then only the males grow wings.
“These are weird bugs” Sadof said.
A single female can lay between 3,000 and 4,000 eggs that hatch young insects that Sadof has taken to calling “crawlers.”
The crawlers literally go wherever the wind blows them, occasionally hitching rides on passing birds in hopes of landing on a suitable tree, where they can latch on, feed and hibernate for the winter before continuing the cycle.
The tulip poplar, Indiana’s state tree since 1931, is a preferred feeding ground for the scales.
If a tree’s branches and surroundings, including sidewalks and cars, are coated with a blackish, sugary, sticky substance, called honeydew, scales are somewhere in the vicinity.
This year, infestations are easy to find.
“This year is the largest I’ve seen this issue,” said Mike Ferree, an extension educator with the Bartholomew County Purdue Extension Office.
Normally, rain washes away the honeydew before most people notice it and helps to keep the pests in check, but watering trees also helps, Ferree said.
“When it’s really dry it gets to be a sticky miss,” Sadof said.
“Maybe this is nature’s way of telling us we have to water those trees,” he said.
While mostly an annoyance, scales in large numbers can threaten trees already weakened or stressed by unrelated ailments.
How does one get rid of the scales?
If a tree is only mildly infested, you can probably wait for nature to take its course. In a few weeks, natural predators such as wasps and pyralid moth larvae provide some relief for affected trees, Sadof said.
Extreme infestations, as the kind that have been cropping up this spring, particularly in the southern half of the state, can be treated with conservative spot pruning or insecticides containing the active ingredient imidacloprid, he said.
Insecticides should be applied to the bare ground around the tree trunk two or three days after it is thoroughly saturated with between four and 10 gallons of water, depending on the size of the tree, Sadof said.
It may take a few weeks before the insecticides take effect as the chemicals have to travel through the tree’s root system and into its sap to reach the scales.
Now is a good time to use the insecticides, Sadof said, because the tree flowers are beginning to fade and there’s little danger of poisoning bees that feed on them.
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