PDC, University of Missouri - Dieback and Decline

Plant Disease Profile

Dieback and Decline of Shade Trees and Shrubs

(See also MU Publication G5200, Tree Decline -- What is it?)

Cause: Tree and shrub decline is a progressive deterioration in the health of a tree or shrub that is attributed to a combination of factors. These may include environmental stresses such as extremes in temperature or moisture, site problems such as soil compaction, extremes in soil pH, poor soil texture for plant requirements, mechanical injuries to trunk or roots, insect infestations and diseases such as defoliating leaf diseases, root rots and wilt diseases. While each of these factors alone may not be that detrimental to the plant, in combination they may cause the decline and death of the plant. The plant, in order to compensate for this stress, will decrease the amount of top growth to restore the delicate balance between the branches and roots.

Primary Hosts In Missouri: Sugar maples and many species of oaks are commonly affected, but other trees and shrubs may also decline. No plant species is completely immune to the problem.

Symptoms / Diagnosis: There is an overall loss of vigor (see photo). Early fall coloration of leaves, late leafing in spring, production of foliage in clumps, decrease in twig growth (see photo), heavy seed crop production, and twig dieback are all symptoms. These visible symptoms may not occur until the tree or shrub is severely stressed. A declining plant will also be more susceptible to other disease and insect problems.

Integrated Management Strategies: Prevention and early detection are the key to keeping trees and shrubs healthy. Plant in favorable environments and avoid stresses. Keep soil pH mildly acidic for oaks. Avoid unnecessary injury. Water deeply during dry periods. Mulch over the root system to maintain an adequate level of soil moisture and to promote root growth. Once the plant is in a state of decline, it will be necessary to restore the natural balance of roots and shoots by pruning 10 to 20% live branches as well as all dead and dying branches. Use fertilizers high in phosphorus and low in nitrogen to stimulate root growth. Prevent serious recurrent defoliating disease with fungicide treatments and treat serious insect and mite infestations.

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Email: plantclinic@missouri.edu

Cause:	Tree and shrub decline is a progressive deterioration in the health of a tree or shrub that is attributed to a combination of factors. These may include environmental stresses such as extremes in temperature or moisture, site problems such as soil compaction, extremes in soil pH, poor soil texture for plant requirements, mechanical injuries to trunk or roots, insect infestations and diseases such as defoliating leaf diseases, root rots and wilt diseases. While each of these factors alone may not be that detrimental to the plant, in combination they may cause the decline and death of the plant. The plant, in order to compensate for this stress, will decrease the amount of top growth to restore the delicate balance between the branches and roots.
Primary Hosts In Missouri:	Sugar maples and many species of oaks are commonly affected, but other trees and shrubs may also decline. No plant species is completely immune to the problem.
Symptoms / Diagnosis:	There is an overall loss of vigor (see photo). Early fall coloration of leaves, late leafing in spring, production of foliage in clumps, decrease in twig growth (see photo), heavy seed crop production, and twig dieback are all symptoms. These visible symptoms may not occur until the tree or shrub is severely stressed. A declining plant will also be more susceptible to other disease and insect problems.
Integrated Management Strategies:	Prevention and early detection are the key to keeping trees and shrubs healthy. Plant in favorable environments and avoid stresses. Keep soil pH mildly acidic for oaks. Avoid unnecessary injury. Water deeply during dry periods. Mulch over the root system to maintain an adequate level of soil moisture and to promote root growth. Once the plant is in a state of decline, it will be necessary to restore the natural balance of roots and shoots by pruning 10 to 20% live branches as well as all dead and dying branches. Use fertilizers high in phosphorus and low in nitrogen to stimulate root growth. Prevent serious recurrent defoliating disease with fungicide treatments and treat serious insect and mite infestations.

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	Email: plantclinic@missouri.edu