Diagnosing Tree Disorders in the Landscape

1
Diagnosing Tree Disorders in the Landscape
2
What is a plant disease?

• Anything that damages plant health
• Plant pathology deals with infectious organisms
  that reduce plant health, multiply, and spread
  biotic diseases

3
Plant Diseases

• Biotic Factors
• Viruses
• Bacteria
• Fungi
• Nematodes
• Abiotic Factors
• Environmental Problems
• Herbicides
• Nutritional Deficiencies
• Pollutants

4
Damage from herbivores

• Animals and Rodents
• Insects
• Mites
• Nematodes

5
Insect Damage Identification

• Know Common Pest Arthropod Groups!
• Numerous lepidopteran caterpillars (ex.
  armyworms, cutworms)
• Beetles (Order Coleoptera) numerous
  leaf-feeding and wood-boring pests
• Sawflies (Order Hymenoptera)
• Various flies (Order Diptera)
• Various insects with piercing-sucking mouthparts
  including scales, mealybugs, whiteflies, aphids,
  psyllids, hoppers, various other members of the
  Order Hemiptera.
• Spider Mites

6
Symptoms vs. signs

• Symptoms are changes in growth or appearance of a
  plant in response to a damaging factor
• Signs are evidence of the damaging factor

7
Symptom or sign?
8
Diagnosis

• Compare plants with disorder to healthy plants
• Roots, stems, leaves, fruits
• Ask questions!
• History, conditions, variety, soil, etc.
• Hypothesis of cause

9
Diagnosis - Continued

• Look for signs of pathogen
• Microscopic examination
• Culturing on artificial media
• Immunological methods (ELISA, etc)
• Nucleic acid methods (PCR, etc)
• Electron microscope
• Look for signs of insect or animal
• Organism itself, eggs
• Frass
• Honeydew
• Webbing

10
What questions do you ask?

• History herbicide application, fungicide
  application, insect activity
• Pattern isolated plant, entire field, near
  edges, etc? Any spread?
• Any variety differences?
• Certified planting stock?

11
What are viruses and viroids?

• Very small particles of nucleic acid and protein
  (viruses) or naked nucleic acid (viroids)

12
Symptoms of Viruses
13
Plum Pox Virus
14
Bacterial diseases

• Bacteria are single-celled, prokaryotic organism
  (lack a membrane around the nucleus of the cell)
• Most plant pathogenic bacteria are gram negative,
  which means they do not retain the stain crystal
  violet when you do a gram stain
• LPS (lipopolysaccharide) layer around cell wall

15
What do bacteria look like?

• Cant see with the naked eye unless there are a
  LOT of them
• Culture on artificial media (some are not
  culturable on media)

16
Bacterial disease symptoms
17
Fire blight

• Erwinia amylovora
• Apple, pear, mountain ash, raspberry, hawthorne,
  contoneaster

18
What are fungal diseases?

• Cause the majority of economically significant
  plant diseases
• Caused by fungi organisms with threadlike
  hyphae and reproductive structures (spores)

19
Fungal Plant Diseases

• Root Diseases - Soilborne and Residue borne
• Cankers
• Rots
• Wilts
• Foliar Diseases Residue borne, wind-blown and
  rain-splashed spores
• Leaf spots and leaf molds

20
Fungal symptoms signs
21
Dutch Elm Disease in Montana
Beetle Galleries
Lesser European Elm Bark Beetle
Staining in twig
22
Cytospora canker - Spruce
23
Verticillium Wilt
24
Root Rots and Diseases
Wind-thrown Trees
Phytopthora
Armillaria
25
Sudden Oak Death Phytopthora ramorum
26
Rhizosphaera needle cast

• Rhizosphaera kalhkoffii
• Rainsplash dispersed
• Symptoms
• Reduced needle retention
• Dead (brown) older needles
• Healthy, new needles do not show signs of
  infection

27
Powdery mildew
Obligate Parasite Spores airborne over
long distances
28
Nematodes a very small, worm-like animal
29
Pine Wilt Nematode
30
Piercing Sucking Insects

• Insects with piercing-sucking mouthparts cause
  stippling and/or chlorosis on the host.
• Example groups aphids, true bugs, hoppers,
  scale insects, whiteflies

Aphids
Plant Bugs
31
Sooty Mold
32
Leaf miners
birch leafminer

• Insects that produce characteristic mines in
  leaves by feeding.
• Formed by various insects including flies, wasps,
  moths, and beetles.

33
Leaf Defoliaters

• Damage caused to a plant by insect feeding.
• Skeletonizing results when the veins or the
  skeleton of the leaf is left behind.

Grasshoppers
Japanese Beetles
34
Spider Mite Damage

• Leaf damage includes flecking, bronzing,
  and/or scorching of leaves.
• Several natural enemies. Most problematic
  in heavy insecticide use areas.

twospotted spider mite
35
Damage by Boring Insects

• Insects that bore into a stem, or seedhead
• Damage often results in weakening or killing the
  host

36
Emerald Ash BorerWhat does the damage look like?

• Canopy starts to thin and water sprouts may start
• Serpentine feeding just below bark
• Small, D-shaped exit hole
• Woodpecker damage another clue to infestation

37
Emerald Ash BorerWhat does it look like?

• Adult is metallic green, about ½ inch
• Larvae are flat bodied, about 1 inch
• Larvae pupate in the tree and adults emerge from
  D shaped exit holes

38
Cottony Ash Psyllid
39
Woodpeckers and Sapsuckers
40
Porcupines
41
Deer and Elk Rubs
42
Drought Damage

• Trees will shed leaves and needles to prevent
  water loss

43
Herbicide?

• History
• Soil analysis or bioassay
• Tissue analysis

44
Symptoms of herbicide injury
45
Winter Injury
Frost Damage
Desiccation
46
Seasonal Needle Cast
47
Planting too deep
48
Iron Deficiency - Chlorosis
Common in high pH Soils

• Apply sulfur to lower soil pH
• Apply chelated iron fertilizer
• foliar or soil applications

49
How to be a diagnostician

• Know the plant involved
• What a healthy plant looks like!
• Look for symptoms and signs
• Look for patterns
• Question the environment
• Make a diagnosis, and check the facts!

50
Montana State UniversitySchutter Diagnostic Lab

• Physical address
• 121 Plant BioScience Bldg. (PBB)
• Mailing Address
• 119 Plant BioScience Bldg.
• P.O. Box 173150
• Bozeman, MT 59717-3150
• [phone]
• diagnostics_at_montana.edu
• http//diagnostics.montana.edu/