Honeylocust plant bug, Diaphnocoris chlorionis, causes damage when the insect’s mouthparts penetrate the leaf cells and injects a toxic saliva while feeding. This toxic saliva, which helps with the uptake of plant cell contents and digestion, kills cells around the feeding site causing browning, leaf rolling, distortion, and chlorosis. Damage can weaken the tree, causing it to be more susceptible to attack by secondary insects and diseases. After the plant bugs are gone, the damaged leaves will remain on the plant for the rest of the season.
In early spring, newly emerging leaves should be examined for active nymphs, stippling, and distortion symptoms prior to treatment. If nymphs are present, insecticides should target young nymphs 7 to 10 days after bud break. If using contact sprays, be sure to cover the foliage and bark completely.
Other Treatment Practices
- Trees grown in exposed, sunny locations are more susceptible to plant bug attack.
- Nymphs may be sprayed off the leaves with high-pressure water.
- Yellow-leaved varieties such as ‘Sunburst’ seem to more susceptible to this pest.
- Planting green-leaved varieties such as ‘Skyline’ can help to decrease susceptibility.
Treat with Xytect in late summer/fall for plant bugs. These insects are active early in the spring of the year. A spring soil treatment with Xytect will miss the window of opportunity for same season control.
Signs of Damage
- Yellowish-white leaf stippling on upper surfaces that eventually turns brown
- Leaf rolling, distortion, and chlorosis
- Chlorotic spots turn brown, and entire leaf dries and drops
- Severe infestations may lead to complete defoliation, but death rarely occurs
- Adults are pale green and about 1/8 inch long with a four segmented antennae and mouthpart that is beak shaped
- The nymph looks just like the adult, but smaller
- Both adults and nymphs are very active and can be seen flying when tree branches are disturbed
- Eggs are light in color and nearly 1/8 inch in length
Photo: Whitney Cranshaw
Colorado State University, Bugwood.org
Photo: Oregon State Uni. Bugwood.org
Trees At Risk
- Just after bud break in early spring, young nymphs crawl into unfolding leaves and begin feeding (58-246 GDD).
- Nymphs feed for 3-4 weeks before maturing.
- Adults mate and lay eggs.
- Eggs overwinter as eggs imbedded in the bark.
Always refer to product label for rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments.