Decline in Ash Trees: Diseases & Environmental Stresses An Identification Guide

Author(s): Laurie Stepanek
Photo of ash tree in decline.
Many diseases and environmental stresses contribute to the decline of ash trees in Nebraska. This publication describes the common characteristics of these problems.
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General symptoms of decline

• Yellowing
• Wilting
• Leaf scorch
• Sparse foliage
• Stunted twig growth
• Late leaf emergence
• Early fall coloration
• Dying branches
• Epicormic shoots, water sprouts, suckers (shoots sprouting directly from the trunk or major limbs)
• Increased susceptibility to insects and diseases

Poor Sites and Drought

Ash trees naturally grow near streams and rivers where moisture is plentiful and shade and natural leaf litter protect and cool the roots.

Ash planted in landscapes or windbreaks often are located in relatively hot, dry sites and given little or no supplemental water. Such conditions stress trees and lead to decline.

Proper watering and mulching with woodchips can help alleviate stress.

Herbicide Injury

Symptoms include twisted, cupped, curled or stunted leaves; defoliation; branch dieback; and sometimes tree death.
Control: identify the source of the herbicide and prevent repeat exposure.

Girdling Injury

Girdling restricts the flow of water, nutrients, and sugars in the trunk and branches.

Vascular Diseases

Affect the tissues that carry water, sugars, and nutrients within trees.

Not easy to diagnose because they usually do not cause unique symptoms.

No chemical controls for these ash diseases.

Decays and Cankers

Decays and cankers are diseases of the trunk and branches.

Branch dieback is a common symptom.

Trees with extensive decay and dieback may be hazardous.

Minor Ash Pests

Some pests of ash affect the appearance of trees but usually cause little serious damage.

These minor problems rarely require control.