Why do my ash leaves look blotchy and twisted?

Ash plant bug nymphs feeding on young leaves cause speckling, blotches and twisting.

Usually not; mature trees aren't harmed.

Ash Plant Bug: Blotchy, Speckled Ash Leaves in Spring

Adults are oval, up to 1/4 inch, more slender than the nymphs, with wings over the abdomen.^[1]
Nymphs are up to 1/8 inch, pale yellow or red to brown or black, like large mobile aphids.^[1]
Both leave small black, sticky droppings under leaves.^[1]

Look-alike	How to tell them apart
Ash anthracnose	If leaves drop in spring, the cause is usually ash anthracnose or stress, not plant bugs.^[1]

It feeds on green, white and black ash.^[1]

US map: public records from 14 states since 1990 (GBIF).

Eggs hatch as ash leaves expand; first-generation adults appear in June and second in July or August.^[1]

Second-generation eggs overwinter in bark and bud scales; there are two generations a year.^[1]

Feeding makes tiny yellow spots that merge into blotches; leaves may twist, brown and look scorched.^[1]
The first generation does more damage because young leaves are more sensitive.^[1]

It feeds on ash only; Minnesota Extension mentions no risk to people.^[1]

Ignore and tolerate the damage in most cases.^[1]

If needed, insecticidal soap or pyrethrins on spring nymphs work on contact; later sprays are less effective.^[1]

Why do my ash leaves look blotchy and twisted?: Ash plant bug nymphs feeding on young leaves cause speckling, blotches and twisting.^[1]
Do I need to treat?: Usually not; mature trees aren't harmed.^[1]

University of Minnesota Extension, “Ash plant bugs (Yard and garden insects).” extension.umn.edu/garden-and-home/yard-and-garden/yard-and-garden-insects/ash-plant-bugs (accessed 2026-10-06)
iNaturalist, “Tropidosteptes taxon page (order and family).” www.inaturalist.org/taxa/358317 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.