Deciduous trees are raining sap

Asked July 26, 2013, 10:51 PM EDT

We have aspen and locust trees raining sap all over. They did not used to do this. Help! The bottoms of our shoes are sticky, the driveway is sticky and we can't see out of the car windows unless we wash them each day.

Deschutes County Oregon trees and shrubs insect issues

1 Response

Hi, The "sap" that is coming down from the trees is actually not coming from the tree but from aphids (an insect) that are on the leaves of the tree. As they feed they excrete honeydew, a clear, sweet sticky substance. The ants and wasps love it as a food source so you may be noticing them as well. Initially you will want to take a garden hose and just spray down the trees as best you can. The jet spray will knock down some of the aphid population immediately and help relieve some of the dripping. You can do this repeatedly to keep the population at bay until some long term management kicks in. For this you use any of the following: http://pnwhandbooks.org/insect/hort/landscape/common/landscape-pests-aphid

If the trees are larger, a systemic would work best. The active ingredient imidacloprid(look for that as the active ingredient) is a systemic that can be used for the aspen. Aspen are wind pollinated not insect pollinated so there is no risk to our bee population from this insecticide. The locust is pollinated by insects so you may want to consider using a different option for this one. Be sure and read the label and follow the directions accordingly to any insecticide you choose to use.

Feel free to call me at the number below for more information. Thanks,