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