Ash plant bug

Need to know

  • A common sap-feeding insect pest that attacks both green and white ash trees.
  • They appear in late June or early July, are green to light brown in color and have a distinctive yellow triangular spot in the middle of the back. 
  • Puncture wounds produced by feeding cause white speckles which will eventually coalesce into broad chlorotic areas, which may turn brown and the leaves drop prematurely. 
  • Control is seldom warranted, and dropped foliage is easily replaced in healthy trees. 

Description of ash plant bugs

Adult ash plant bugs appear in late June or early July.  They are 1/4 inch long, slender bugs that are green to light brown in color and have a distinctive yellow triangular spot in the middle of the back.  Nymphs are tiny, active, and light green to black in color.

Life cycle of ash plant bugs

These insects overwinter as eggs on the bark of trees.  The eggs begin to hatch as the buds break and the foliage emerges in the spring.  Tiny green nymphs crawl to the undersides of leaves and begin a feeding period that lasts approximately five weeks.  New adults then lay eggs for a second generation of nymphs that feed during the second half of the summer.

Damage caused by ash plant bugs

Puncture wounds produced by the feeding action of the bugs cause discrete white speckles on the upper surface of the leaves.  Individual speckles eventually coalesce into broad chlorotic areas on heavily infested trees, which may turn brown and the leaves may drop prematurely.  The undersurface of infested leaves are marked with shiny black specks of excrement called varnish spots.


Management of ash plant bugs

Control of the ash plant bug is seldom warranted.  Foliage lost because of damage from this bug is easily replaced by healthy, vigorous trees.  Also, by the time damage is noticed it is usually too late for effective control.  The best management for ash plant bugs is to maintain tree health and vigor through watering and mulching.

If you have stressed or newly transplanted trees, insecticides can be used.  Timely treatment while the nymphs are still small can prevent feeding damage symptoms.  Begin checking ash tree foliage for nymphs at the time redbud trees in your neighborhood are beginning to bloom.

Do you live in Iowa and have an insect you would like identified?

The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them.  Please see our website for current forms, fees, and instructions on preserving and mailing insects.   

Contact information for each state's diagnostic laboratory for U.S. residents.  If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.  

Last reviewed:
November 2021

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on September 12, 2016. The information contained within may not be the most current and accurate depending on when it is accessed.