Tropidosteptes amoenus

Ash plant bug damage. (Image: Whitney Cranshaw, Bugwood.org)
Scientific Name: Tropidosteptes amoenus
Common Name: Ash Plant Bug
Growing Degree Days (GDD's): Approx. 120–700 GDD's, Base 50°F, March 1st Start Date (Source: Robert Childs, UMass Extension.)
Host Plant(s) Common Name (Scientific Name)
Ash (Fraxinus spp.)
Green ash (Fraxinus pennsylvanica)
White ash (Fraxinus americana)
Insect Description:

Two generations per year. Eggs are laid in cracks and crevices of host bark in the fall, where they overwinter. Eggs hatch in mid-May. Nymphs crawl to the undersides of the leaves where they will feed. Adults of the first generation will lay eggs on the midveins of the leaves in the summer (July) and eventually hatch to produce the second generation of nymphs. Second generation plant bugs will feed on the underside of leaves until killed by the frost, laying the eggs that overwinter on host bark. Tropidosteptes amoenus is an eastern species that is now considered widespread due to horticultural commerce. Several different species of plant bug feed on ash in other areas of the US.
Damage to Host:

Foliage of many ash species. Most feeding occurs on leaf undersides. May cause leaf discoloration or leaf drop when populations are heavy. When young ash leaves are fed upon, the damage from this insect might cause severe deformation of the leaf or dwarfing. Damage may first be noticed on the leaf surface as yellow-white stippling that may eventually coalesce to form larger chlorotic (discolored) areas. 
Monitoring:

Look for stippling from plant bug feeding on the leaves in the spring. Damage may be noticeable any time from when the insects begin to feed, until the first frost.
Cultural Management:

Ash plant bug feeding damage is primarily aesthetic. Healthy hosts planted on the proper site can generally withstand ash plant bug feeding. Tolerate and ignore the feeding damage, especially for the second generation of plant bugs which may cause less damage than the first spring generation.
Natural Enemies & Biological Control:

None noted, but as a native insect in North America, presumably some natural enemies exist. 
Chemical Management:

Acephate (NL)

Acetamiprid (L)

Beauveria bassiana (NL)

Bifenthrin (NL)

Carbaryl (L)

Chlorpyrifos (N)

Chromobacterium subtsugae (NL)

Clothianidin (NL)

Cyantraniliprole (NL)

Cyfluthrin (NL)

Deltamethrin (L)

Dinotefuran (NL)

Flonicamid+cyclaniliprole (N)

Gamma-cyhalothrin (L) 

Horticultural oil (L)

Imidacloprid (L)

Insecticidal soap (NL)

Isaria (paecilomyces) fumosoroseus (NL)

Lambda-cyhalothrin (L)

Neem oil (NL)

Permethrin (L)

Pyrethrin (L)

Spinetoram+sulfoxaflor (N)

Tau-Fluvalinate (NL)
Notes:

When used in nurseries, chlorpyrifos is for quarantine use only.

Active ingredients that may be applied systemically (injected) include: acephate (L, injection), acetamiprid (injection), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), imidacloprid (soil drench), and neem oil (soil drench).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022 neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: September 27, 2024. To check current product registrations in Massachusetts, please visit the MA Department of Agricultural Resources Pesticide Product Registration page and click on "Search Pesticide Products Registered in Massachusetts - Kelly Solutions".