Honeylocust Plant Bug

Honeylocust Plant Bug (Diaphnocoris chlorionis) - Affecting Honeylocust trees

                      
If your honeylocust trees look like these on the left in June, don't feel bad.   Most Cheyenne honeylocust trees look like this every spring. The trees will push out another set of leaves about a month later, as seen in the photo on the right of same trees.
Photos: Cheyenne Urban Forestry

                                                          
                       A closer look at the damage on the leaves.                    The culprit - Honeylocust plant bug
                                                     Photo: E. Bradford Walker                                                                        Photo: Whitney Cranshaw
                                                     through Forestry Images.                                                                          through Forestry Images.

The honeylocust plant bug is very small, half the size of a grain of rice.  The insect overwinters in the egg stage.  The eggs hatch at the time the trees break bud, (new leaf growth), usually late April through early May.  The feeding occurs for about one month.  At the end of May to early June, the adults are present for two to three weeks.  During this time they mate and lay eggs for the next year's generation.  There is only one generation per year.

The feeding of the honeylocust plant bug during spring leaf emergence causes the tree to use limited food storage to develop a new set of leaves, usually late June to early July.  Spring defoliation of the tree year-after-year severely weakens the tree, causing limb die-back, sometimes to the point of tree death.

The trees can be sprayed at bud-break, or soon after bud-break, to help control the insect. OR Merit® a brand name systemic insecticide containing Imidacloprid can be injected with water into the root zone of the tree.  The insecticide is taken up by the roots and spreads throughout the tree, killing many types of insects feeding on the tree.  The honeylocust leafhopper, cottony maple scale, and aphids can also be controlled using an Imidacloprid product.  An application of Imidacloprid can be effective for a year or more.  It should be applied to the root zone while the tree is in full leaf.  An application in mid to late summer should still be effective at bud-break the following spring.  The application of Imidacloprid should be left to commercial pesticide applicators.

Links:

Colorado State University Cooperative Extension

University of Wyoming - Cooperative Extension Service, publication B-1035 is particularly helpful for tree care. This online publication contains information on: Aphids, Borers, Cottonwood blotch leaf miners, Cytospora canker, Fireblight, Gall makers, Aspen leaf spots, Oystershell scale, Pear slugs, Powdery mildew, and Spider mites.