The Nebraska Forest Ser vice: Enriching l ives by protect ing, restoring and uti l i z ing Nebraska ' s tree and forest resources .

FH21-2014

www.nfs.unl.edu

N E B R A S K A F O R E S T S E RV I C E

Decline in Ash Trees:Diseases & Environmental Stresses An Identification GuideLaurie Stepanek, Forest Health Assistant

Many diseases and environmental stresses contribute to the decline of ash trees in

Nebraska. This publication describes the common characteristics of these problems.

General symptoms of decline•Yellowing•Wilting•Leafscorch•Sparsefoliage•Stuntedtwiggrowth•Lateleafemergence•Earlyfallcoloration

•Dyingbranches•Epicormicshoots,watersprouts,suckers(shootssproutingdirectlyfromthetrunkormajorlimbs)

•Increasedsusceptibilitytoinsectsanddiseases

Epicormic shoots

Scorch

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Poor Sites and Drought

Herbicide Injury

Soil cracks:•Unwateredtreesarefrequentlystressed.•Dailywateringorwateringeveryotherdayisalsostressful.•Droughtaddstotheproblem.

Ash in parking lots:•Hotconcreteorasphalt.•Restrictedrootingspace.•Rockmulch(absorbsheat).•Weedbarrier(limitsoxygenandmoisturemovementintothesoil).

Stressful site:•Compacted,drysoil.•Exposedroots.•Nowoodchipmulcharoundthetree.

Healthyashleaf

•Treerootscanpickupherbicidesfromthesoil.1

•Exposuremayoccurfromherbicidesappliedalongafence,onsidewalksordriveways,aroundutilities,orfromlawnherbicides.

Distorted,stuntednewgrowth.2

9Symptoms include twisted, cupped, curled or stunted leaves; defoliation; branch dieback; and sometimes tree death. 9Control: identify the source of the herbicide and prevent a repeat exposure.

Herbicidedamage

9Ash trees naturally grow near streams and rivers where moisture is plentiful and shade and natural leaf litter protect and cool the roots. 9Ash 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. 9Proper watering and mulching with woodchips can help alleviate stress.

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Vascular Diseases

Girdling Injury

"Mower blight":•Missingbarkanddamagedinnertissues.•Causedbymowersandstringtrimmers.•Grassgrowingnexttothetrunkinvites"mowerblight."

9Girdling restricts the flow of water, nutrients and sugars in the trunk and branches.

•Twine,string,wire,orhoseleftontreescancauseinjury.•Donotstaketreesmorethanayear.

Girdling roots:•Maybeaboveorbelowsoil.•Oftendevelopbecausetreesgrewinapotfortoolong.

Verticillium wilt3:•slowgrowth•sparsefoliage•wilting•yellowing•scorching•defoliation•branchdieback•treedeath

Ash yellows4:•Symptomssimilartoverticilliumwilt.•Clustersofspindleyshootswithsmallleaves("witches'-brooms")sometimesappearatthebaseofthetreeoronthetrunk.

9Affect the tissues that carry water, sugars and nutrients within trees. 9Not easy to diagnose because they usually do not cause unique symptoms. 9No chemical controls for these ash diseases.

The Un ivers i t y o f Nebraska-L inco ln i s an equa l oppor tun i ty educator and employer.

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Decays and Cankers 9Decays and cankers are diseases of the trunk and branches. 9Branch dieback is a common symptom. 9Trees with extensive decay and dieback may be hazardous.

Decaymushrooms(conks)maybefoundonthetrunkorbranchesoratthebaseofthetree.

Decaysandcankersofteninfectthroughpruningcuts.

Branchdieback.

•Hollowtrunksandbranchesresultfromdecay.•Notetheepicormicshoots.

White mottled heart rot

Sulfur mushroom

Photo credits:

1: Steven Ramaekers, Nebraska Tree Works Inc.2: Swift Horticultural Enterprises LLC3, 5: Iowa State University4: Joseph O'Brien, US Forest Service, Bugwood.org6, 7: Whitney Cranshaw, Colorado State Univ, Bugwood.org

9Some pests of ash affect the appearance of trees, but usually cause little serious damage. 9These minor problems rarely require control.

A.AshanthracnoseB.Ashrust5

C.AshflowergallD,E.Ashleafcurlaphid6

F.Ashplantbug7

A B C

E FD

Minor Ash Pests

See also: “Decline in Ash Trees:

Borers and Bark Beetles.”FH20-2014

Nebraska Forest Servicenfs.unl.edu