Midterm Core Content

Sign

Physical evidence of a casual agent of disease. Ex. Mushrooms

Symptom

The visible effects that are expressed by a diseased tree. Ex. Necrosis or hypertrophy

Decline

Reduction of growth quality either in whole or part.

Necrotic

Mortality of any region of the plant.

Hypertrophy

Excessive growth in any region of the plant.

Atrophy

Reduced growth in any region of the plant.

Chlorosis

Loss of green colour in leaves due to an ability to produce chlorophyll.

Predisposing factor - decline

Long term factors that are inherent characteristics of the site such as climate, soil moisture, soil nutrients and air pollutants or the genetics of the host.

Inciting factor - decline

Short term factors or events that aggravate the predisposing conditions such as insect defoliation, frost, drought, salt, air pollutants, and mechanical injury.

Contributing factor - decline

Long term factors such as bark beetles, cankers, viruses and decay.

Injury

Stresses that cause abnormal physiological effects from short term or singular events. Ex. Leaf mortality due to sudden frost in June.

Disease

Stresses that are reoccurring and are generally progressive in nature. Ex. Beech bark disease

Symptomology

The study of disease symptoms.

Biotic causal agents

Symptoms are uneven, progressive, host specific, and infectious resulting in a clumping pattern.

Abiotic causal agents

Symptoms may or may not be plant specific, uniform, not progressive, not host specific, and has a random distribution pattern.

Ascomycete fungi

Causes leaf diseases, vascular wilts, and cankers.

Basidiomycete group

typically causes bracket fungi, rusts and root diseases.

Three categories of rusts

1. Canker rusts (white pine blister rust)

2. Gall rusts (Western gall rust)

3. Leaf rusts (conifer-aspen rust)

Conifer-aspen rust (Primary host)

Poplars Ex. trembling aspen and cottonwood

Conifer-aspen rust (Alternate host)

Conifers

Pine-needle rust (Primary host)

2 and 3 needle pines

Pine-needle rust (Alternate host)

Goldenrod and aster

Spruce needle rust (Primary host)

White sprue, black spruce, and red spruce.

Spruce needle rust (Alternate host)

Labrador tea and leatherleaf

Life cycle of white pine blister rust (Stage 1)

Basidiospores (n) produced in late summer on ribes species.

Life cycle of white pine blister rust (Stage 2)

After 2-3 years of infection, canker with yellow blisters forms in the summer.

Life cycle of white pine blister rust (Stage 3)

Aeciospores (n+n) are produced the following spring on the canker area. The canker sites turn dark rough and swollen before bursting. Spores infect the leaves of surronding ribes species through the wind.

Life cycle of white pine blister rust (Stage 4)

Stage 3 repeats and more aeciospores (n+n) re-infect species a few weeks after the initial infection.

Life cycle of white pine blister rust (Stage 5)

In late summer of that same year teliospores (2n) are created in cold, damp weathers. These teliospores germinate and produce haploid basidiospores (n) that infect pines.

Most commercially important canker diseases.

1. Chestnut blight

2. Hypoxylon canker

3. Beech bark disease

4. Butternut canker

How do root diseases spread?

Through root to root contact with an infected tree., spread through mycelium. Or spread by rhizomorphs in the soil. Weakened trees are more susceptible.

Compartmentalization of Decay in Trees (CODIT) Theory

How the tree defends itself against decay: Walls are created to separate decayed areas from healthy areas.

Wall 1: Changes happen in vessels surrounding the wound.

Wall 2: Changed in the cells of the interior growth ring to the wound occurs to protect the heartwood from the decay.

Wall 3: Ray cells are altered around the perimeter of the wound.

Wall 4: New growth is created around the exterior of the wound to protect new and healthy tissue.

Brown rot tree decay

Has a brown and cubical colour. Is comprised of most lignin.

White rot tree decay

Has a bleached white a fibrous colour. All components have been removed including cellulose and lignin.