The honey locust plant bug (Diaphnocoris chlorionis) is approximately 1/8 inch long and pale to light green when full grown. There are three stages: eggs, nymphs and adults. The nymph is a miniature replica of the adult.
The honey locust plant bug overwinters on honey locust as an egg beneath the bark of twigs and branches. The eggs hatch in the spring, just as the leaf buds begin to open. Young nymphs begin feeding on the young foliage at this time causing damage to the emerging leaves. Nymph development requires 30 days, so adults will appear by late May or early June. The adults continue to feed for one to two months and disappear by mid-to late July. Eggs are laid by the adults in linear clusters under the bark of 2- and 3-year-old twigs. There is only one generation per year.
Feeding by the honey locust plant bug results in leaf distortion, chlorosis, and yellow-to-brown spots. Heavy plant bug infestations may cause premature leaf drop, but typically a second flush of leaves is produced. Despite the damage to the foliage, trees do not die. They will be stressed if feeding occurs several years in a row. Unfortunately, the honey locust plant bug is an unpredictable pest because weather conditions influence the bug’s survival and activity. An outbreak one year does not ensure an outbreak in subsequent years.
Maintaining tree vigor by watering and fertilizing as needed is probably the best way to ensure tree health. Contact the Plant Clinic (630-719-2424 or email@example.com) for current recommendations. Use pesticides safely and wisely; read and follow label directions. The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.