Weeping Cherry Tree Insects

Asked June 30, 2019, 1:52 PM EDT

Help! I have a Weeping Cherry tree and there are hundreds of black ants crawling around on leaves and leaf stems. Also, there are a number of gold-colored houseflies that seem to be just sitting on leaves (not flying around). I have sprayed the tree with a solution of water+vegetable oil+dish soap+rubbing alcohol to deter Japanese Beetles (which seems to be working! So far - so good...) Are the ants harmful to the tree? There are holes in a good share of the foliage, but the tree seems to be healthy. Thanks in advance. Tom M

Ingham County Michigan

1 Response

Ants on a cherry tree (or any other landscape plant for that matter) are usually a sign that the tree has an aphid infestation. The ants care for the aphids, protect them from predators, etc. A good solution to this problem is to exclude the ants. You can use a sticky barrier such as an insect trap coating (e.g. TAD®, Tanglefoot®) around the base of the tree to exclude the ants. Check for aphid colonies on the underside of the leaves and/or on the leaf petioles. Sometimes simply spraying the underside of the leaves with a good hard spray from you garden hose will dislodge enough of the aphids, especially if you prevent the ants from returning the fallen aphids to the tree.
The "gold-colored house flies" are probably the adult stage of an insect called a syrphid fly. Syrphids lay their eggs near aphid colonies and their larvae eat the aphids.