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Verticillium Wilt

Infects

Hundreds of plant species including trees.

Symptoms

Infection of the plant starts in the roots and then moves throughout the tree.

Verticillium wilt has acute and chronic phases. Acute and chronic symptoms often occur at the same time on one plant.

  • When symptoms appear in the sapwood, dark streaks or bands that follow the grain may be present. This symptom may be absent in the early stages of infection.
  • Acute symptoms include curling, drying, abnormal red or yellow colour of leaves, defoliation, wilting, dieback, and death. Yellowing and defoliation often progress upward. These symptoms may be restricted to one branch or involve the whole plant. Symptoms appear from early summer into autumn on the current season growth. Plants may have acute symptoms on consecutive growing seasons or may skip one or more years. In between, depending on the severity of the infection, the plant may appear normal, or one or more branches may show chronic symptoms.
  • Chronic symptoms include slow growth, sparse foliage, stunted leaves and twigs, scorched leaves, abnormally heavy seed crops, and dieback. Chronic symptoms indicate stress caused by the previous death of sapwood and are confined to wood at least one year old.

Cause

Verticillium wilt is caused by a fungus that originates in the soil.

The fungus invades woody tissue of plants and causes death or disfigurement of hundreds of plant species.

Cure

Newly infected trees showing wilt on a few branches can be saved by applying a large dose of a high nitrogen fertilizer early in the growing season and pruning affected areas below the point of infection.

Trees showing general or severe wilt infection cannot be saved. They should be removed and the wood burned or taken to the landfill to be disposed immediately.

IPM Toolkit

Preventive tools

  • Sterilize your pruning equipment with methanol (gas line antifreeze) between cuts.

Physical tools

  • Not applicable

Biological tools

  • Not applicable

Chemical tools

  • Not applicable