We have a oak tree which seems to be discharging
sap from it. It appears to be coming down on occasions like fine
rain. Is this normal, and could you explain what is going on?
When you describe your situation like observing a "fine rain", it sounds to
me as if there may be an aphid infestation. Simply put, aphids feed by
sucking sap from various tree species; in turn, when they release thier
waste, called honeydew, it often ends up coating things like car windows,
etc. situated beneath the affected trees.
On occasion, trees will emit sap after injuries, e.g. getting hit by a lawn
mower, but your "fine rain" description sounds more like the aphid problem I
You can call your county extension agent, located in the city which is the
county seat for your county. If you describe your situation to them in
detail, they may have pamphlets with recommendations which can be mailed to
you. Alternatively, you can google "aphid" to see if their honeydew is what
you are seeing, or you can visit a local college or public library which
likely contains either botanical texts or those dealing with care of trees,
identifying insect and disease pests.
Thanks for using NEWTON!
Click here to return to the Botany Archives
Update: June 2012