Principles of Plant Pathology and Important Forest and Range Diseases in Idaho

1. Principles of Plant Pathology and Important Forest and Range Diseases in Idaho Presented by Dwight Scarbrough Entomologist USDA Forest Service Forest Health Protection March 19, 2013 Edition Oxford Suites, Boise, Idaho, USA Presentation Developed by James Hoffman Plant pathologist (Retired)

2. Section 1: • Introduction to the Basic Principles of Plant Pathology. Presentation Outline Section 2: Important Plant Pathogens in Forest and Range Ecosystems in Idaho. • Section 3: • Decline Diseases: A Complex of Biotic and Abiotic Origins. • Section 4: • Hazard Trees and Your Safety.

3. Section 1:Introduction to the Basic Principles of Plant Pathology

4. What is a Plant Disease? • A disturbance that interferes with a plant’s “normal” structure, function, or physiological processes. • As opposed to a tree injurywhich is caused by a single event (e.g. hatchet blow to a tree)

5. Disease Definitions • Parasite– an organism that lives on or • in another organism. • Host– an organism that provides • nutrition for an invading parasite. • Pathogen– an agent that causes • disease.

6. Disease Triangle Disease is the product of three interacting factors Host Plant Disease Environment Pathogen

7. Signs of Diseases • The physical presence of the pathogen on the surface or inside the plant • Fruiting bodies, fungal tissues, dwarf mistletoe shoots, etc. • Geeks look for spores (under a microscope)

8. Symptoms • The expression of the host to the pathogen infection. • Tissue death, abnormal growth forms, branch or top-dieback, lesions, yellowing, decay, defoliation, etc.

9. Is this a diseased cottonwood tree? No, it’s early fall!

10. Types of Diseases Tree Disease Concepts, Paul D. Manion Biotic diseases (Infectious) Abiotic diseases (Non-infectious) Decline diseases - (Complicated as many pathogens are involved over a long time period.)

11. Types of Biotic Diseases (Infectious plant disease agents) • Fungi • Parasitic Plants • Bacteria • Mycoplasmas = Phytoplasmas • Virus • Nematodes • Others?

12. Types of Abiotic Diseases (Non-infectious plant disease agents) • Moisture imbalances (Drought) • Wind • Temperature • Nutrient and mineral imbalances • Air pollution • Soil acidity or alkalinity • Others?

13. Common Categories of Fungal Diseases • Foliage diseases • Cankers (usually stem rusts) • Decays and Rots • Root diseases • Vascular wilts

14. Management Techniques for Plant Diseases • Regulatory Methods • Quarantines and Inspections • Cultural Methods • Host Eradication • Rotation to Non-host Species • Sanitation • Altering the Environmental Conditions • Biological Control • Chemical Control • No Control

15. Section 2:Important Plant Pathogens in Forest and Range Ecosystems in Idaho

16. Foliage Diseases • Needlecasts • Needle Blights • Shoot Blights • Mostly caused by fungi • Cause spotting and discoloration • Cause premature defoliation • May reduce growth • Only a problem when infection occurs over consecutive years

17. Signs of Foliage Diseases Snow Blight • Signs • Fungal fruiting bodies are often visible on the surface of infected needles Lophodermium needle cast Elytroderma needle cast

18. Symptoms of Foliage Diseases Pine needle cast • Leaf spots or discoloration • Dead/dying foliage • Thin crowns • Degrees of Defoliation Dothistroma needle cast

19. Lodgepole pine Needlecast

20. Other Foliage Diseases Elytroderma Needlecast Marssonina Leaf Spot of Aspen Snow Mold

21. Elytroderma Small, dense witches’ brooms

22. Cedar-apple RustGymnosporangium sp. Orange “Jello” on Junipers in spring Galls on junipers in fall

23. Control of Foliage Diseases • Control usually not needed nor is it practical • Maintain mixed species composition in stand • Maintain healthy, vigorous trees • Role of fire? • High value trees– both protective and controlling fungicides

24. Cankers – a symptom of disease • Localized area of dead bark or cambium • Often sunken because the tree continues to expand around the infection site • Very common • More common on thin-barked species (aspen) • Usually caused by fungal infections that enter through wounds

25. Identifying Cankers Hail damage

26. Fungal Canker Symptoms • Expanding edges • Callus ridges and sunken wood • Dead wood inside margin Black knot of cherry 12 Cytospora canker Target canker

27. Signs of Cankers • Sometimes fruiting bodies are invisible

28. Cankers of Aspen • Often perennial & expand until the tree is girdled • Most important & common group of diseases in aspen • Cause direct mortality • Provide entry point for decay fungi

29. Rust Galls and Cankers • Cause diseases of leaves branches and stems • Rust colored spores • All require a living host (obligate parasites) • Complex lifecycle often involving 2 different plant hosts and up to 5 spore stages!

30. Western Gall Rust • Most common canker in pines in this area • A “pine-to-pine” rust • Causes hip cankers that rarely girdle the tree • Wind-snapping at canker is common • Fungus enters through needles

31. Western Gall Rust Attacks all 2-3 needle pines: ponderosa, lodgepole, scots, and Austrian pines.

32. Western Gall Rust - Hip cankers on stems create weak areas…

33. White Pine Blister Rust • Introduced from Europe in the early 1900’s • Lethal, invasive disease • Infects all species of white, 5-needle pines • In Central Rockies this would be limber, whitebark, and bristlecone pines • Alternate host = currants and gooseberries

34. Symptoms of White Pine Blister Rust • Cankers are often gnawed on by rodents • Swollen cankers with orange margins • Roughened bark as a result of past fruiting • Branch death (flagging)

35. Signs of White Pine Blister Rust • Resinous, diamond shaped cankers on branches/stems • Orange blisters and spores that infect the alternate host

36. White pine blister rust in the Central Rockies2005

37. Other Rusts • Comandra Blister Rust • Common and important in lodgepole and ponderosa pines • Infects all hard pines • Causes top-kill • Spruce and Fir Broom Rust • Common but do not cause serious damage

38. Decays (Rots) Top rot, usually resulting from top breakage or damage Stem or trunk rots Butt rot Root rot

39. White Rot • Fibrous, usually whitish • Break down lignin leaving some cellulose intact • Variable appearance Brown Rot • Brown in color, cubical, crumbly • Breaks down cellulose leaving lignin

40. Indicators of Decay • Infection courts • Fire scars, logging scars, broken/dead tops, fallen trees, old-growth characteristics • Symptoms • Exposed decay, cracks, decayed branch stubs, sparse foliage, cavity nesting birds • Signs • Conks, fruiting bodies fungal tissues, carpenter ant activity

41. Stem Decays • Decay in trees • Generally in inner wood • aka “heart rot” • Caused by fungi, that often form conks (sign)

42. White Trunk Rot (Phellinustremulae) • On aspen only • White rot • Most infected trees have conks Conks

43. Saprots • “Pouch” fungus – insect correlation • In the sapwood • On dying or newly killed trees Cryptoporousvolvatus “pouch fungus”

44. Root Diseases • Most involve decay of the roots and lower stem  “root and butt rots” • Hard to Diagnose • Symptoms are nonspecific, not diagnostic, and may not appear • Greatest concern • Structural failure (snapping, uprooting) of green trees!

45. Root Disease Spread Airborne: by spores Subway: root-to-root

46. Signs of Root Disease -Fruiting Bodies Phaeolusschweinitzii The “cow-pie” conk

47. Symptoms of Root Disease Basal resinosis Thin crown, stress crop, branch dieback

48. Symptoms of Root Disease Expanding mortality centers Decay in roots

49. Vascular Wilts • Mostly caused by fungi • Invade conducting tissues, disrupt water movement, and cause wilting • Infect wounds on stems or roots • Diagnoses based on symptoms

50. Black Stain Root Disease • Pinyon pine in CO, ID, UT, NV • Vectored by insects • Trees develop thin, chlorotic crowns • Expanding infection centers • Black streaks in roots