Linden Tree Honeydew Solution

Q: I have a huge 30 year old Linden tree, and when I park my car underneath it, I end up with the car speckled with something sticky. What is that from? Someone said from aphids? Or is it the tree itself?

Aphids are sucking insects, but technically speaking they simply plug their mouthparts into the vein of a tree and let a steady stream of sweet sap flow into their bodies. Since the sap contains lots of sugar and not much of the building-blocks needed by the aphid to make protein, the aphid consumes much more sap than it needs. Most of this flows right out the other end of the aphid, hence the sticky substance all over the tree (its own sap via an aphid). It is known as “honeydew.”

I watched this process on a large maple tree near my home last spring and was interested in the result. After a few weeks of dripping trees, an army of ladybugs (also called ladybird beetles) moved in and began to eat the aphids. Their young larvae look like little dragons and they ate even more aphids. Then came a few parasitic wasps to finish them off. Within a few weeks there were no significant numbers of aphids. We had a heavy rain and all the sticky honeydew was gone and the trees looked fine.

While aphids can be a problem on smaller plants, distorting leaves and flowers, on a large tree like a linden they won’t do any damage. Since it is water based, the honeydew can be rinsed off your car regularly until the problem diminishes. You could use a systemic insecticide, but I prefer to let nature take its course.