Marisa Thompson, Ph.D.Extension Horticulture Specialist

New Mexico State University

Diagnosing Tree

Symptoms

Website:www.desertblooms.nmsu.edu

Weekly Gardening Column:nmsudesertblooms.blogspot.com

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Causal Agents of Disorders• Biotic • Abiotic

Causal Agents of Disorders• Biotic

• Fungi• Bacteria

Causal Agents of Disorders• Biotic

• Fungi• Bacteria• Viruses• Nematodes

Image: William M. Brown, Jr., Bugwood.org

Causal Agents of Disorders• Biotic

• Fungi• Bacteria• Viruses• Nematodes• Insects & Mites

Causal Agents of Disorders• Biotic

• Fungi• Bacteria• Viruses• Nematodes• Insects & Mites• Humans

Causal Agents of Disorders• Biotic

• Fungi• Bacteria• Viruses• Nematodes• Insects & Mites• Humans

• Abiotic• Soil moisture extremes• Temperature extremes• Salts• Air pollution• Wind, light effects• Mechanical damage• Pesticide damage• Old Age

Diagnosing Disorders• The process of determining the cause of an abnormality

• Diagnosis is a team effort• Owner/Manager• Consultant/Advisor/Extension Agent• Diagnostic Clinic/Specialist

• Conclusions are derived from critical evaluation of the tree and the environment

• Requires a blend of good observational skills, science, and experience

Diagnostic Advice• Don’t jump to conclusions

• Keep an open mind

• Be a detective: observe, question, gather clues

• Evaluate the whole plant, the whole yard, and the areas around the problem area

• When possible…• Dig up and look at roots• Cut open stems, branches, fruits, etc.

The First Step: Spot the Problem

• Diagnosis begins with the observationthat there is a problem with the tree(s)

• Know the healthy/normal appearance (cultivar diffs)

• Symptoms

• This means you need to physically be around your trees on a regular basis.

SymptomsSymptoms usually develop because the causal agent:

•Produces (or induces the plant to produce) enzymes, toxins, or growth regulator imbalances

•Interferes with specific cellular functions• The particular symptom develops based on

whatever plant process(es) are affected

The Difficulties with Symptoms

• Change over time (progression)• Vary with severity/virulence of the stressor/pathogen

• Vary due to age or stage of the tree• Vary due to environmental conditions during and after infection

SYMPTOMS ARE OFTEN INSUFFICIENT FOR DIAGNOSIS

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''I typed in your description of the symptoms. The computer says you

have Dutch elm disease."

Symptoms are Complex!• Symptoms are not always specific to causal agents

• Causal agents often affect more than one plant process at a time leading to complex symptomology

• Plants may be affected by more than one causal agent (abiotic and biotic) at a time

• adds to complex symptomology

SYMPTOMS ARE OFTEN INSUFFICIENT FOR DIAGNOSIS

Symptom Could be Caused by a Secondary Problem

• Primary problem –directly responsible

• Secondary organisms –taking advantage of weakened plant tissue

• Saprophytes – a non-pathogenic microorganism residing on the plant and feeding on decaying organic matter

Abiotic disorders often predispose the tree to biotic disorders!

•Biotic• Fungi• Bacteria• Viruses• Phytoplasma• Nematodes• Insects & Mites

•Abiotic• Soil moisture extremes• Temperature extremes• Salts• Air pollution• Wind, light effects• Mechanical damage• Pesticide damage

OFTEN PREDISPOSE TO BIOTIC!

Abiotic disorders often predispose the tree to biotic disorders!

•Biotic• Fungi• Bacteria• Viruses• Phytoplasma• Nematodes• Insects & Mites

•Abiotic• Soil moisture extremes• Temperature extremes• Salts• Air pollution• Wind, light effects• Mechanical damage• Pesticide damage

Cypress very hard hit by heat(Poor planting technique, crummy mulch, and landscape fabric didn’t help much)

Photos: Richard Buckley, NJAES

You Did What!?!

Distinguishing between Abiotic Disorders and Plant Diseases

Abiotic Disorders Plant DiseasesMay affect several species Usually one species affected or

like species affected

Cooperative Extension Service

Photo Credit: Julie Day, www.dannylipford.com

single species = probably disease

multiple species = probably not disease

Distinguishing between Abiotic Disorders and Plant Diseases

Abiotic Disorders Plant DiseasesMay affect several species Usually one species affected or

like species affectedSymptoms often develop suddenly

Symptoms usually develop slowly

Cooperative Extension Service

sudden symptom development = probably not disease

Photo credit: Jeff Anderson, NMSU-CES

Distinguishing between Abiotic Disorders and Plant Diseases

Abiotic Disorders Plant DiseasesMay affect several species Usually one species affected or

like species affectedSymptoms often develop suddenly

Symptoms usually develop slowly

Symptoms do not spread Symptoms spread from plant to plant

Cooperative Extension Service

Slow and progressive symptom development = probably disease

Distinguishing between Abiotic Disorders and Plant Diseases

Abiotic Disorders Plant DiseasesMay affect several species Usually one species affected or

like species affectedSymptoms often develop suddenly

Symptoms usually develop slowly

Symptoms do not spread Symptoms spread from plant to plant

Distribution may be uniform or patterned

Distribution is random (scattered, clustered, sporadic)

Cooperative Extension Service

All plants rapidly decline after a week above 100oF

Photo: Richard Buckley, NJAES

Heat and Drought Stress

The Second Step: Gather accurate and complete information

•Situation•History of the Disorder•Spatial Variability•Symptom Expression

Tree-in-wall Disease1993 19991993

Critical Information Needs• Situation

– Species/Cultivar– Age and production history– Soil textures – Cultural practices:

• irrigation, fertilizers, pesticides…– Weather conditions before and during symptom

development– Historic land use– Land use in adjacent properties– Soil and water analyses– Leaf tissue nutrient analyses

Boxwood Freeze Injury

Ruh Roh!?!Who?

What?

Why?

When?

How?

Critical Information Needs

• History of the Disorder:• When the problem began. Or when symptoms were

first noticed.

• Whether it is a chronic problem

• Whether the symptoms are spreading (within tree or to other plants in the orchard)

Critical Information Needs

Critical Information Needs

• Spatial Variability of the Disorder:• Percentage of trees affected

• Pattern of symptoms• Scattered • Clumped • Random

• Other plants affected

Critical Information Needs

• Symptom expression• The plant parts affected• Top-down or bottom-up in canopy• Where is PRIMARY site of injury?

The progression in severity on plant over time

Evaluating Leaf Symptoms• Uniformity or patterns?

• Leaf and plant• Size of spots

• Margin (borders)?• Thickness• Color

• Spread or growth?• Edge definition• Merging of spots

• Fruiting bodies?

The Third Step: Collect Specimens

• Important for accurate diagnosis• All specimens should be fresh, kept refrigerated

• Submit samples showing all stages of problem

Sampling: Include samples from all affected organs

• Do not destroy signs or symptoms

• Roots: Remove soil, include tissue above and below visible lesions

• Stem and leaf: Include tissue above and below visible lesions

• Flower, fruit, seed: Collect the entire organ

Example of Actual Leaf Sample

Photo: Natalie Goldberg, NMSU

Online Resources

http://fruitsandnuts.ucdavis.edu

Online Resourceshttp://www.ipm.ucdavis.edu

Online Resources

Facebook Groups

The Entomology Group – 120,387 members

Plant Identification & Discussion – 232,540 members

Online Resources

https://aces.nmsu.edu/ces/plantclinic/

NMSU Plant Diagnostic Clinic

Blognmsuplantclinic.blogspot.com

NMSU Plant Diagnostic Clinic

Sampling Techniques:Handling and Packing

• Identify/label correctly every specimen • Package delicate material in a sturdy box

• Do not add water or wet paper towels• Ship immediately overnight and early in the week

Google search: “Colorado State Extension Insects and Diseases of Woody Plants in Colorado”

Marisa Thompson, Ph.D.Extension Horticulture Specialist

New Mexico State University

THANKS!

Website:www.desertblooms.nmsu.edu

Weekly Gardening Column:nmsudesertblooms.blogspot.com

Social Media@NMDesertBlooms