WSU Extension

Hortsense

Willow : Marssonina leaf & twig spot
(revision date: 4/28/2014)


Biology
Marssonina leaf and twig spot is a fungal infection of twigs and leaves. Initially, small brown to black spots develop on leaves and green twigs. The spots may have white centers. On twigs, the spots may expand to form large girdling lesions which cause twig dieback. The fungus probably overwinters on infected and dead twigs and in fallen leaf debris. This disease rarely does severe damage, although it can be an aesthetic problem.
Management Options

Non-Chemical Management
  • Prune and destroy infected twigs if practical. Disinfect pruning tools after use.
  • Rake and destroy any fallen leaves from beneath willow trees, particularly in the fall, to reduce reinfection risk.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images
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Caption: Marssonina leaf and twig spot
Photo by: R.S. Byther