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. icosahedral rods flexuous rods geminivirus tospovirus viroid inclusion body 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? • Can’t 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 (406) 994-5150 diagnostics@montana.edu http://diagnostics.montana.edu/