WSU Extension


Honey locust
Honeylocust canker 
Powdery mildew 
Honeylocust pod gall midge 
Locust borer 

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Honey locust : Powdery mildew
(revision date: 4/28/2014)

Powdery 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.
Management Options

Non-Chemical Management
  • Plant in sunny locations.
  • Space trees and prune to provide good air circulation.
  • Clean up and destroy fallen leaves from beneath infected trees. Powdery mildew can overwinter in infected leaf debris.
  • Provide proper culture. Do not overfertilize, as succulent new growth late in the season is particularly susceptible.
  • Prune and destroy severely infected twigs and branches to reduce spread of disease.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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