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Is that sap falling from the trees?

“Are those sticky droplets falling from the trees, landing on me and my bike and my car, really sap?”

This reference question made me feel just a little bit gross inside once I found out the answer. The substance dripping from cottonwoods around campus did indeed begin as sap, but went through the digestive tract of an aphid before it landed on you, your bike, and your car. Aphid specialists call it “honeydew“. To which I say “honey ewwwwww”.

Aphids visited by black garden ants (Lasius niger) and brimming over with honeydew.

Photograph taken in The Hague by Jens Buurgaard Nielsen

This entry was posted on Tuesday, August 26th, 2008 at 1:01 pm and is filed under Library News. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

2 Responses to “Is that sap falling from the trees?”

  1. Toni says:
    August 26, 2008 at 1:30 pm

    Thanks-I’ve been wondering that too.

    And eww!

  2. Abby says:
    August 26, 2008 at 1:42 pm

    I have a question ;) So I noticed that a lot of the cottonwood leaves look a bit ill. Not only are they dripping “honey ewww” but there are dead spots on the leaves with a dark center. Does anybody know whats plaguing our cottonwoods?