Aspen trees raining

Asked August 30, 2019, 6:42 PM EDT

We have been experiencing a drought and I notice the Quaking Aspen are dropping a substance that looks just like a varnish. Is this a protective mechanism? Or is it something that happens when a drought occurs. We had a very severe drought last year followed by a deep snow year, followed by a dry summer.

San Juan County Utah

1 Response

Either your aspen or a nearby tree has aphids that are feeding on the sap in the leaves. They insert their stylet (a feeding tube) into the leaf and the sap actually is pressurized so it flows into their bodies. They take in what they can, but most of the sap passes through their bodies and out the other end and little droplets fall on whatever is under the tree. This material is called honeydew, and if you taste it you will find that it is sweet. When it dries it forms a shiny surface at first that may eventually get mildew on it and turn dark. It is easy to wash off with water and does little harm to the tree or to the surfaces it lands on.