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Honeylocust plant bugs

Quick facts 

  • Honeylocust plant bug and leafhopper only feed on honeylocust trees.
  • They pierce leaf tissue and feed on sap. 
  • Tolerate the damage, as it only affects tree appearance. 
  • Trees grown in exposed, sunny locations are more prone to plant bug attack.
  • Varieties of honeylocust with yellow leaves are more attractive to honeylocust plant bugs than the ones with green leaves.
  • Young, recently transplanted trees will have more damage.

Honeylocust plant bug (Diaphnocoris chlorionis) and the honeylocust leafhopper (Macropsis fumipennis) can be mistaken for each other. They belong to a group of insects that are found on shade trees in Minnesota.

How to identify honeylocust plant bugs

A smaller pale green nymph and a larger pale green adult honeylocust bug on a green honeylocust leaf
Honeylocust plant bug nymph (left) and adult (right)
  • Honeylocust plant bug nymphs and adults are oval and range up to 1/8" long as nymphs and ¼" long as adults.
  • Both nymphs and adults are pale green and blend in with leaves.
  • Adults have fully functional wings whereas nymphs do not.
  • Nymphs are very active and will climb onto anything that may come in contact with the foliage.
  • Nymphs are sometimes described as looking like large, mobile aphids.

Life cycle

  • Honeylocust plant bugs have one generation per year.
  • Eggs can survive through the winter to hatch in spring, when the honeylocust leaf buds start opening up.
  • It takes about one month for plant bugs to mature from egg to adult.
  • The newly hatched nymphs climb onto the new leaves and feed until June when they mate and lay eggs in clusters under the bark of young twigs.
  • They remain there until the following spring.
  • Adults are rarely seen after late July.
  • Eggs do not hatch for the rest of the year until the following spring.

Damage caused by honeylocust plant bugs

Twisted honeylocust leaves with discolored patches
Deformed foliage caused by honeylocust plant bug feeding
  • These bugs feed with a needle-like mouthpart (stylet) on the underside of leaves.
  • They remove the plant fluid and release the saliva into the leaf.
  • Damage from saliva creates tiny, circular and discolored patches on the leaf (stippling).
  • Damaged leaves remain small and become twisted and dwarfed.
  • The damage looks similar to herbicide injury. But, honeylocust plant bug damage is seen on new leaves all across the plant, and herbicide damage occurs only on the side where herbicide was sprayed.
  • The bugs also produce small, shiny, dark, varnish-like droppings on the undersides of infested leaves.

In most cases, damaged leaves remain on the tree until the fall season. If the damage is severe, the leaves will fall off, especially in younger trees.

How to protect your trees 

Check for plant bugs in early spring

Check trees for honeylocust bugs, when new buds start to come up. This is especially important, if they have been found on your trees in the past. If insect numbers are high enough, insecticide applications might be required.

Using pesticides

Pesticides should be applied only if it is necessary to protect the appearance of the tree or when the health of the tree is at risk.

  • Good coverage and timing is critical.
  • Spray the undersides of the leaves where plant bugs are normally found

The best time to apply a pesticide is when it is budding. Applying pesticides later might not be as effective.

For applying pesticides on large trees, it is better to contact a professional tree care service provider.

  • Insecticidal soap is a low impact pesticide that can be effective against nymphs.
    • The spray has to come in direct contact with the nymphs to be effective.
    • Repeat applications of these soaps can be necessary.
  • Broad spectrum, stronger pesticides are also available, like:
    • Permethrin
    • Bifenthrin
    • Carbaryl
    • Acephate

Be careful while using broad spectrum pesticides. They might kill beneficial insects, along with the honeylocust plant bugs. Broad-spectrum pesticides can kill the predators of spider mites and can cause a spider mite outbreak.

Honeylocust flowers are very attractive to bees when they are blooming. Avoid pesticides like imidacloprid and dinotefuran as they are toxic to bees.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Jeffrey Hahn, Extension entomologist

Reviewed in 2018

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