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SPRUCE DISEASES: HERBICIDE SYMPTOMS OR NOT?

Garden Saturday, February 2, 2008Kasia KinzerKasia KinzerPlant DiagnosticianNDSU Plant Diagnostic Lab

Overview

NDSU Plant Diagnostic Lab statsWh t i Di ?What is Disease?

Definition of diseaseWhat are biotic causes of disease?What are abiotic causes of disease?Tips on distinguishing between biotic and abioticcauses in general

Spruce DiseasesSpruce DiseasesWhat causes symptoms on spruce?

Tips on how to differentiate possible diseases caused by plant pathogenic fungi from chemical injury or other abiotic causes of symptoms

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Lab Trivia: Tree diagnoses NDSU Plant Diagnostic Lab 2007

Total tree diagnoses in 2007: 150 Deciduous: 88Evergreen: 62

Total spruce diagnoses: 55Blue (Colorado Blue): 12Black hills spruce (white): 2Black hills spruce (white): 2Species not specified: 41

More Lab TriviaNDSU Plant Diagnostic Lab 2007

Most common spruce problems:Abi ti 36Abiotic: 36

Winter injury (8)Mechanical injury (5)Chemical injury (4)‘Environmental stress’ (19)

Biotic: 23Stigmina needle cast (5)g ( )Cytospora canker (2)Rhizosphaera needle cast (1)Spider mites (6)Aphid, needleminer, borer, or sawfly (5)

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What is Disease?

Any malfunctioning of host cells and Any malfunctioning of host cells and tissues resulting from continuous irritation by a pathogenic agent or environmental factor leading to development of symptoms

– Agrios

Host Pathogen

Disease

Environment

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Infectious (Biotic)

Non-Infectious (Abiotic)

Causes of Diseases

FungiArthropodsVirusesBacteriaNematodes

Nutrient deficiency or toxicityMoistureTemperatureLight

( ) (Abiotic)

And so on(arthropods, too)

pHMechanicalHerbicide injuryOther Chemical injury

What are symptoms and signs?

Symptomsresponse of plant (what the plant looks like)

Examples: wilting, needle discoloration, dead branches

Signsphysical presence of organism (or its parts) that causes disease

Examples: insect bodies, castings, frass; fungal vegetative or fruiting bodies

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Examples of Symptoms

Yellow tips on needlesbrown inner needles

canker, excessive sapwilted new growth

Examples of Signs

fungal fruiting bodies

fungal fruiting bodiesactual pest

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Herbicide Symptoms or Not?

Characteristics of Biotic C

Characteristics of AbioticCCauses Causes

Symptoms AND signs typically present; may need lab work to induce signs

Symptoms only

Can spread within a plant over time Usually do not spread within a plant

Can spread from one plant to another

Usually do not spread from one plant to another (some exceptions)

Can worsen over time Usually do not worsen over time

Pattern within a tree may be non-uniform

Pattern within a tree or among trees may be uniform, sided, discrete

Symptoms usually appear gradually Symptoms may appear all at once

Herbicide Symptoms or Not?

Many symptoms can understandably be f d ith ibl h bi id i jconfused with possible herbicide injury

Symptoms from different causes look similarLook for mechanical injuryLook for root disturbancesLook for evidence of arthropod feedingLook for environmental stressorsLook for environmental stressors

Look for BOTH symptoms and signs to confirm a diagnosis of a BIOTIC disease

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Diseases of Spruce

Common biotic diseases:Needle cast diseases

Rhizosphaera needle castStigmina needle cast

Cytospora cankerCommon abiotic problems:

“E i t l t ”“Environmental stress”Winter injuryMechanical injuryChemical injury

Needle Cast Diseases

Rhizosphaera needle castRhizosphaera needle castCaused by Rhizosphaera kalkhofii

Confirmed in North Dakota in early 1990s

Stigmina needle castCaused by Stigmina lautii

First diagnosed in North Dakota in 2006Probably present prior to 2006

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Needle Cast Diseases

Symptoms are similar:Discoloration of inner needles (not current growth)Needle loss (inner needles; not current growth)Lower portions of tree affected first; can progress upwardDoes not normally kill budsDoes not normally kill buds

Severe cases can kill buds of lower branches

Needle Cast DiseasesSigns are superficially similar

Signs of Rhizosphaera kalkhoffi Signs of Stigmina lautii

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Needle Cast DiseasesManagement of Rhizosphaera needle cast

M b t d f hi h l May be warranted for high value treesFungicides (e.g. chlorothalonil; Bordeaux mixture):

First application: when new needles are 50% normal lengthSecond application: 3-4 weeks later when needles are fully elongatedwhen needles are fully elongatedMust be applied for at least two consecutive years

No recommendations available for Stigmina needle cast

What else can cause browning of inner needles?

Biotic causes, such asFeeding by arthropods in a previous year (e.g. aphids, mites)

Abiotic causes, such asExposure to a toxin in a previous yearExposure to a toxin in a previous yearDrought stress in a previous yearNutrient deficiency in a previous year

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Cytospora cankerCaused by a fungus: Cytospora sp.Symptoms

Brown and dying needles on a branch (usually lower branches first)Branch dies (bud is dead)Excessive bluish-white sap

SignsSignsFruiting bodies just under bark at canker

ManagementPrune out infected branches in late winter or during dry periods

Cytospora Canker - Symptoms

Note individual dead branches here and thereBuds of dead branches are d d dead

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What else can kill buds?

Abiotic diseases, such asSevere winter injuryGirdling by mechanical injuryHerbicide injuryShading out of lower branches

Biotic diseases in addition to Cytospora Biotic diseases, in addition to Cytospora canker

Boring insects

Abiotic diseases of Spruce

Winter dessicationFrost injuryHerbicide injury

Look for patterns

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Winter Desiccation

Can be confused with herbicide injuryNote brown needles at top half of trees, above the snow lineAffected branches not necessarily dead (depends on severity)

Spring Freeze Injury

Can be confused with herbicide injuryBackground information needed

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Herbicide injury

Note spiral pattern of dead branchesNote very ‘clean’ lawn (no weed to be found!)

Herbicide injury – suspected

Note sided nature, fairly uniform distribution throughout tree, including upper canopyToo young for needle

t di cast disease or Cytospora cankerNo evidence of mechanical injury

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What damaged these trees?

More information is More information is needed …

Look at the Big Picture

Note healthy trees in backgroundNote healthy weeds in foregroundNote cultivation (spruce have shallow root systems)Root disturbance seems more likely than chemical injury in this scenario

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Herbicide injury or not?Provide or obtain as much information as possible, such as

When and how was tree plantedHow often is tree wateredWhat surrounds the tree (fields, lawn, etc)How old is the treeAre different species affected similarlyChemical history of lawn and nearby fields

Wh did t fi t d th When did symptoms first appear, and are they spreading or getting worse

Note pattern of symptoms in treeLook for any other cause of symptoms

Herbicide injury or not?

Usually based on visual evaluationCan sometimes narrow possibilities into a few chemical familiesNot always definitive!

Chemical analysis sometimes warrantedBut this can be costly!But this can be costly!Helpful to have an idea of chemical familyPrivate and public chemical testing labs available

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If you want help, or if you suspect chemical injury:

Take lots of good quality picturesg q y pDocument as much as possible (handout)Consult local expertsConsult county extension agentsBring sample to a diagnostic lab such asBring sample to a diagnostic lab, such asNDSU Plant Diagnostic Lab206 Waldron Hall701-231-7854

Thank You!

NDSU Plant Diagnostic Lab Website: www.ag.ndsu.nodak.edu/diaglab(contains info on services available and fees, and has a partial list of chemical analysis labs in the Midwest)