FOREST DISEASES AND FOREST HEALTH ESRM 101 Spring 2007 Bob Edmonds 264 Bloedel

Alex Shigo

TOPICS 1. Natural disturbances in ecosystems 2. The concept of forest health 3. Causes of disease 4. Types of diseases 5. Impacts of tree diseases 6. Impacts of management on diseases 7. Management of diseases Great websites

1. Natural disturbances in ecosystems - caused by disease, fire, insects, wind, flooding, volcanic eruptions

Crown fire in interior west forests

Natural recovery of lodgepole pine forests 5 years after the Yellowstone wildfire. Note carpet of young seedlings.

Unhealthy forests in eastern Oregon and British Columbia - high mortality due to bark beetles and root diseases

2. CONCEPT OF FOREST HEALTH Healthy people and individual trees do not have diseases, but healthy ecosystems can have dead and dying trees (important habitats for organisms

A healthy old-growth forest ecosystem in Mt. Rainier National Park Note dead trees (snags)

- a healthy ecosystem should be free from “distress syndrome,” where the syndrome is characterized by reduced primary productivity, loss of nutrient capital, loss of biodiversity, increased fluctuations in key populations, retrogressions in biotic structure, and widespread incidence and severity of diseases, insects and fires.

Dry Interior west Fire suppression high tree density drought stress root diseases bark beetles defoliators Unhealthy forest

3. CAUSES OF DISEASE - non-biological (abiotic)- air pollution (0zone, acid precipitation), environmental conditions (too hot, too cold, too wet, too dry), nutrition - biological (caused by viruses, phytoplasmas, bacteria, fungi, parasitic plants (mistletoes), nematodes, amoeba) Fungi and dwarf mistletoes are most important in Pacific Northwest forests

ABIOTIC DISEASES

Dead trees at Clingman’s dome, Great Smoky Mountains National Park (left)and Mt. Mitchell, NC (below). Initially attributed to acid rain, but mostly due to the Balsam woolly adelgid Definitely unhealthy

Smog in southern California forests - mostly ozone produced by photochemical oxidation of NOx in auto exhausts

Ozone damage to ponderosa pine in California

Cold temperature injury

BIOLOGICAL DISEASES

Tobacco Mosaic virus

Camellia virus Camelia virus

Rod shaped bacteria

Mold fungus – Penicillium spores

Basidiomycete fungus – conk or fruiting body

True mistletoe on oak in California

Lodgepole pine dwarf mistletoe

Brooms on Douglas-fir caused by Douglas-fir dwarf mistletoe in eastern WA near Leavenworth

Root nematode Pine wilt nematode symptoms Pine wilt nematode

3. TYPES OF DISEASES Foliage diseases Decay of stems and branches Rusts Cankers Wilts Dwarf mistletoes Root rots Wood stains

Defoliation from Swiss needle cast on Douglas-fir SWISS NEEDLE CAST - NATIVE DISEASE

Fomes fomentarius – white spongy trunk rot Hardwoods –birch, alder, poplar

Mortality in white bark pine caused by the introduced white pine blister rust.

Dutch elm disease Wilt disease Chestnut blight Canker disease BOTH ARE INTRODUCED DISEASES CAUSING LARGE-SCALE MORTALITY

Dwarf mistletoe male plants

Laminated Root Rot of Douglas-fir

Blue stain in pine

5. IMPACTS OF DISEASES a. Mortality b. Reduced growth c. Destruction of merchantable wood (decay) d. Reduction in pulp yield e. Reduced wood quality - stain f. Delayed regeneration g. Inadequate stocking (trees/acre) h. Site deterioration - build up of pathogens i. Changes in species succession j. Creation of biodiversity

6. IMPACTS OF FOREST MANAGEMENT ON DISEASES - Forest management has usually made diseases worse. e.g., thinning and clearcutting have generally increased root diseases, However, clearcutting and thinning decreased dwarf mistletoes Fire suppression has increased dwarf mistletoes and root diseases

7. MANAGEMENT OF DISEASES 1.SILVICULTURAL - thinning, fertilization, stump removal for root diseases 2. CHEMICAL - foliage fungicide spraying 3. GENETIC - BREEDING FOR RESISTANCE/ BIOTECHNOLOGY - rust resistance 4. BIOLOGICAL CONTROL -stump treatment to prevent root disease 5. QUARANTINE - great concern about introduced diseases 6. DOING NOTHING

Stump removal for root rot management