young ash tree, curling leaves

Asked June 10, 2020, 12:49 PM EDT

Our young ash tree looks healthy except a few leaves (6?) have recently become very curly. As I looked for insects a bug similar to a silverfish fell off one leaf. Picture #3 is that leaf. Notice the black substance. I don't know what that is other than something possibly excreted by a bug. Do you think I should be concerned? I assume that if many more leaves turn curly I might want to spray with a pesticide. But which one? Thanks for your help. Jim Lodwick

Multnomah County Oregon

1 Response

A suspect in this case is the ash leaf curl aphid. You will be able to tell if this is the case after a while as these distinctive aphids develop further. See https://pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/ash-fraxinus-aphid and https://planttalk.colostate.edu/topics/soils-amendments-composting/1770-ash-leaves-curling/

In the case of these and some other insect problems on ash leaves, the damage is mostly cosmetic and not a major threat to tree health. Insecticide sprays are generally not warranted and also not effective when aphids are inside the curled leaves.