Willow trees can be buzzing with wasps, bees, flies, and other insects during late summer. These insects are probably attracted to honeydew deposits from sap-feeding insects, such as aphids. Good aphid control requires thorough spray coverage with a contact insecticide, such as insecticidal soap. This is difficult to achieve on medium to large trees. Rains and weathering will eventually take care of the honeydew, but it may be necessary to avoid the area while stinging insects are present.
By Lee Townsend, Extension Entomologist