There has been concern regarding sap dripping from oak trees over this last week, appearing on driveways, cars, patios, etc. We have ruled out all commonly known insects, i.e. aphids, etc. that would ordinarily create these symptoms.
Samples have been submitted to Cornell Cooperative Extension and their findings indicate that we are dealing with what they are unofficially calling "Dripping Oak."
This is the first time anything like this has been seen on Long Island, although there is a similar insect and bacterium combination affecting oaks on the west coast. Cornell is attempting to isolate exactly what the pathogens are on Long Island and whether they are the same as the findings on the west coast.
There are no recommended treatments at this time to stop the sap from dripping and the resulting acorn drop. However, there is no current evidence demonstrating that there is any negative effect on the trees. The biggest drawback, other than it being a nuisance, is a loss of some acorns and potential new saplings the following season.
According to experts, once the infected acorns drop the dripping should subside. The exact time frame is unknown at this point. The sap can most easily be washed off shortly after it drops.
We will keep you posted with any new information we receive.