Ash Yellows

Candidatus fraxinii

Key Features

  • Tufted foliage tips
  • Pale leaves drop in summer
  • Clusters of sprouts on branches or trunk
Canopy thinning,William Jacobi, Colorado State University,
Sprouting on trunk caused by ash yellows, William Jacobi, Colorado State University,
Abundant sprouting from the trunk, caused by ash yellows


Ash trees infected by ash yellows experience slow growth, yellowing leaves, tufted leaves at shoot tips, witches brooms shoots, leaf drop, and dieback. White ash typically has more severe symptoms than green ash. Many of the mentioned symptoms can be associated with other conditions such as drought stress or emerald ash borer. Clusters of green sprouts, or witches brooms are a diagnostic symptom of ash yellows, but does not always occur in affected trees. This makes diagnosis difficult and other possible conditions must be ruled out. Please compare with symptoms for "emerald ash borer" which is a growing problem in Eastern North America.

Witches broom caused by ash yellows


The disease cycle of ash yellows is not well known. It is speculated that insects may vector the virus. The disease affects the vascular system (nutrient and water flow) of trees. Other conditions that affect the vascular system (EAB) or conditions associated with reduced nutrient flow (drought) have similar symptoms.

Management Recommendations

There is no current treatment to cure trees of ash yellows. Removal of infected trees is recommended when roughly 25-50% of the tree canopy is dead. Fertilize trees in the fall and water throughout the growing season to increase longevity of the infected trees.

Effective Pesticides

Pesticides are neither available nor recommended for managing this disease.


landscape report
Purdue Landscape Report
Plant & Pest Diagnostic Laboratory