'Sap' causing sticky nuisance around Middle Tennessee
Kim Chaudoin | 615.966.6494 |
Above are sugarcane aphids (the sesame seed-looking objects) found on the leave of a maple tree on campus.
If you’ve parked your car near a tree over the last week or two and noticed a sticky substance on your windows and car doors, you are not alone.
It seems that there is an overabundance of tree sap lately. And there is. But don’t blame the trees. A tiny little insect — the aphid — is the cause of the sticky mess.
“The sap is actually a sugary substance called ‘honeydew’ that is produced by aphids,” says John Lewis, assistant professor of biology in the College of Liberal Arts & Sciences. “This time of year the aphids are reproducing and laying their eggs in the branches of the trees. They are also ramping up their energy supplies for the winter by sucking sap from the trees. They are parasites of the trees. Often they eat more than their bodies can hold. So the sticky substance that we find on our cars and patios is aphid excretion.”
Aphids can produce copious amounts of sticky honeydew. The tiny droplets fall on leaves and anything below such as bedding plants, outdoor decks, furniture, toys, sidewalks, driveways and automobiles.
There are thousands of varieties of aphids, according to Lewis. The sugarcane aphid is commonly found on maple trees, and the white, cotton-like aphids, known as the Asian woolly hackberry aphid, that are frequently seen floating in the air this time of year are found on hackberry trees. Other varieties are found on other bushes, plants and crops.
According to the University of Tennessee Extension Agency, a sooty mold fungi will grow on the sugary substrate and over time turn leaves, bark and other items where the honeydew lands black.
Lewis says that the aphids’ eating the tree sap and the sticky residue left behind isn’t harmful to the trees.
“It’s just a nuisance,” he admits.
The sticky situation won’t last much longer, Lewis promises.
“In a few weeks the leaves will turn beautiful fall colors and they will fall off the trees,” he says, “ and the problem will be in the past.”
In the meantime, Lewis says, a way to avoid the sticky stuff is to park away from trees or to use a pressure-washer to wash the aphids off leaves.
“People want to use insecticides to kill the aphids, but that can also kill beneficial insects,” says Lewis. “About all you can do is try to wash them off the plant, move your car or wait for the leaves to fall.”
Lewis says that water and detergent is effective in removing the honeydew from windows, outdoor furniture and other areas.