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Problem
(factsheet)
Plant NameTypeDescription 
Honeylocust cankerHoney locustDiseaseSeveral fungi are responsible for cankers on honey locust in the Pacific Northwest. One problem, coral spot or Nectria canker, can result in sudden wilting or failure of infected twigs or branches to produce leaves. The slightly sunken cankered area may be indistinct until the fungus sporulates, producing pinkish-orange fruiting bodies that erupt through the bark. Branches may be girdled by the cankers, which are often associated with wounds. Nectria cankers also occur on black locust and many other plants. Both Fusarium sp. and Phomopsis sp. have also been associated with honey locust canker problems in Pacific Northwest nurseries.
Powdery mildewHoney locustDiseasePowdery mildew on honey locust (Gleditsia triacanthos) produces typical symptoms of powdery mildew infections. Leaves and sometimes young shoots are covered with a powdery, gray-white growth. This most often appears in summer and gradually increases throughout the rest of the season. Late in the season, the powdery growth may be dotted with tiny black fruiting bodies of the fungus. Affected leaves may be distorted or stunted, or may drop prematurely.
Honeylocust pod gall midgeHoney locustInsectThe honey locust pod gall midge is a tiny orange gnat that lays its eggs on new foliage in the spring. The small pinkish or yellow-white maggots feed on the leaves, which become deformed, thickened, and pod-like in appearance. The larvae are sheltered inside the deformed leaves. Infested leaves may dry and drop from the tree. Small shoots may be killed. This is mainly an aesthetic concern, since the ornamental quality of the tree may be lost.
Locust borerHoney locustInsectBlack locust (Robinia pseudoacacia) may be infested by the larvae of a boring beetle. Eggs laid in the fall on the bark hatch into larvae which burrow beneath the bark and feed. Symptoms of feeding include swollen, discolored, or oozing patches of bark. Openings in the bark are also present, and piles of debris drop to the ground beneath the openings. The adult is a longhorned beetle about 1/2"-3/4" in length. It is black with yellow markings.