Blepharidopterus (Diaphnocoris) chlorionis

Honeylocust plantbug damage. Photo: Whitney Cranshaw, Colorado State University, Bugwood.
Scientific Name: Blepharidopterus (Diaphnocoris) chlorionis
Common Name: Honeylocust Plantbug
Growing Degree Days (GDD's): 58–246 GDD's, Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name)
Honeylocust (Gleditsia triacanthos)
Insect Description:

Honeylocust plant bug is one of the most impactful (of at least 7 species of) plant bugs on this tree species. There is one generation per year and this insect overwinters as eggs laid just beneath the bark surface of 2 and 3 year old twigs. Eggs hatch once the buds of honeylocust begin to open. Young nymphs will move to the freshly opening leaves and begin to feed. Nymphs (immatures) are pale green with short wing buds that do not extend to the end of the abdomen. The majority of the feeding damage from this insect occurs at this time, while leaves are still very small and the insect is well hidden. Feeding on immature leaves kills their cells, causing often severe leaf distortion or dwarfing. Nymphs develop over a period of 30 days. Adults may be seen by the beginning of June (earlier at points south of MA) and their activity may end in July. Adults are approximately 3/16th of an inch in length and pale green with wings that are held flat against the back. During this time, adult females lay the overwintering eggs in clusters in lines in the bark of twigs.
Damage to Host:

Leaves of new growth on honeylocust are impacted, beginning at budbreak. The immatures and adults feed on the leaves, causing severe distortion, dwarfed leaflets, chlorosis, and yellow or brown spotting. Tiny, irregular holes may be seen as well. Light-moderately damaged foliage may persist through the growing season, however in severe infestations, complete defoliation may occur. Historically (ex. 1995), outbreaks of this insect have caused defoliation in Massachusetts and other parts of New England on its namesake host (Childs, personal communication).
Monitoring:

As soon as leaves begin to unfold in the spring, look for stunting and deformation along with green nymphs on new growth. Scout for adults in June and July. If growing conditions are good, trees may outgrow early season damage from this insect. 
Cultural Management:

Certain cultivars may vary in susceptibility. ‘Summerlace’ may be far less impacted than ‘Skyline’ or ‘Halka’ (Cornell Cooperative Extension). Some sources suggest syringing (spraying the foliage with water) may help dislodge nymphs and knock them to the ground.
Natural Enemies & Biological Control:

No effective parasites or predators are noted at this time.
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)

Spinetoram+sulfoxaflor (N)

Tau-fluvalinate (NL)
Notes:

Active ingredients that may be applied systemically include: acephate (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".