CORNELL COOPERATIVE

EXTENSION OF ONEIDA COUNTY 121 Second Street Oriskany, NY 13424-9799 (315) 736-3394 or (315) 337-2531 FAX: (315) 736-2580

Honeylocust Plant Bugs

Honey locust plant bug has been getting a lot of attention this year because of large numbers of honeylocust (Gleditsia triacanthos) that were late to leaf out. While this insect causes significant dam- age there are many other pests that can disfigure honeylocust. Some of the common pests include honeylocust pod gall midge, mimosa webworm, calico scale and honeylocust spider mite.

If you need to treat for any of these insects on honeylocust keep in mind broad spectrum insecticides can kill natural enemies of the honeylocust spidermite and result in future mite outbreaks. Take that into consideration when reviewing your management options, and if treatment options include horticultural oils, insecticidal soap, spinosad or Bacillus thuringiensis choose one of these. They have little or no impact on spider mites’ natural enemies.

Honeylocust Plant bug (Diaphnocoris chlorionis)

One of the great difficulties in controlling this pest is that it be- comes active almost as soon as the tender leaves begin to emerge. The insects initially hang out within folded leaves where they are well camouflaged and can be easily overlooked.

Hosts Honeylocust only

Description and Life Cycle; The Honeylocust plant bug has one generation per year. It over winters as eggs in the bark of 2-3 year old twigs. As the buds begin to open, the eggs hatch, and the pale green nymphs crawl onto unfolding leaflets where they are subtly visible. They have short wing buds that don’t reach the ends of their bod- ies. By the time they mature as adults-30 days later-they are still pale green but now 3/16 inch long with wings flat on their backs. The adult plant bugs mate and the female lay eggs under the bark of twigs. There the eggs re- main until the following spring

Signs & Symptoms; The most serious damage caused by the Honey locust plant bug occurs as the leaves are be- ginning to unfold. The feeding nymphs and adults causes the leaves to become stunted, deformed and chloritic. Tender leaves are highly susceptible to injury, and most damage is caused by feeding nymphs. According to the University of Massachusetts Extension Specialists, honeylocust plant bugs injury “ is worse in years where cool temperatures prevail for several days soon after bud break and leaf expansion is greatly diminished. During these times, the plant bug can create enough injury to cause defoliation.”

Helping You Put Knowledge to Work

Cornell Cooperative Extension provides equal program and employment opportunities. NYS College of Agriculture and Life Sciences, NYS College of Human Ecology, and NYS College of Veterinary Medicine at Cornell University, Cooperative Extension associations, county governing bodies, and U.S. Department of Agriculture, cooperating. Tiny yellowish to brown spots are apparent. Irregular holes are seen where the necrotic tissue has fallen out. With a large population of plant bugs, trees may be defoliated. If growing conditional are optimal, the honeylo- cust will be able to outgrow early damage and defoliate. Light to moderate damage may continue throughout the growing season..

Management: There are no parasites or predators that provide ‘significant’ control so a pesticide application may be required to manage populations of the honeylocust plant bug. If the nymphs are in abundance, treat in late April through mid may (58-246 GDD). Horticultural oil is excellent for controlling honeylocust plant bug and has the additional benefit of controlling leafhoppers

Early season injury from Honeylocust plant bug damage honeylocust plant bug

This publication contains pesticide recommendations. Changes in pesticide regulations occur constantly, some materials mentioned may no longer be available, and some uses may no longer be legal. All pesticides distributed, sold, and/or applied in New York State must be registered with the New York State Department of Environmental Conservation (DEC). Questions concerning the legality and/or registration status for pesticide use in New York State should be directed to the appropriate Cornell Cooperative Extension Specialist or your regional DEC office. READ THE LABEL BEFORE APPLYING ANY PESTICIDE.

Updated 2006

Information for this fact sheet obtained from http://woodypests.cas.psu.edu/FactSheets/InsectFactSheets/html/Honeylocust.html And Branching out a IPM Newsletter for trees and shrubs Volume 13 No8 July 21,2006