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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)
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