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
Social Media@NMDesertBlooms
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