Lesson 1 Intro to disease

Question 1

Define the Term “Disease”

Answer 1

Disease is the abnormal functioning of a host’s physiology due to biotic or abiotic agent.

Question 2

Define the term Disease “Sign”

Answer 2

Part of the biotic agent associated with disease symptoms (ex spores, fruiting body etc)

Question 3

Define the term “Disease symptom”

Answer 3

symptom is the host’s reaction of the disease.

Question 4

what are some examples of Signs Symptoms and Diseases?

Answer 4

Sign of disease: decay fungus fruiting bodies growing out of tree bark.

Symptom: reduced growth rate, mortality, loss of merchantable wood to rot.

Question 5

Biological agents causing plant disease

Answer 5

1. Bacteria
2. Virus
3. nematodes
4. fungi

Question 6

Linkage between forest disease, insects , and fire

Answer 6

• Insects are a biological agent of disease. bark beetles can carry fungal pathogens into the cambium of a tree when the borrow past protective bark.
• Fire makes trees more susceptible to pathogens.
• pathogens that kill trees also make forests more susceptible to fire events

Question 7

What are Koch’s Postulates (4)

Answer 7

1. Establish constant association of organism and disease symptoms.
2. Isolate organism and grow in pure culture
3. Inoculate healthy plant and produce disease symptoms.
4. Re-isolate organism.

Question 8

What are the 8 Impacts of forest disease

Answer 8

1. Dieback and deformity
2. Stand growth and yield changes.
3. Alters the available merchantable wood.
4. Tree Mortality.
5. Alters species composition.
6. Influences the nutrient cycle.
7. Can make forests more susceptible to other biotic and abiotic disturbances.
8. Lower density of a stand.

Question 9

Why are some disease impacts considered to be positive and negative.

Answer 9

Disease is viewed as negative because it create losses in timber values.

disease is positive as a natural process of the forests. for example, disease can promote creation of habitat by helping create CWD.

Question 10

What is the Pathogen Continuum?

Answer 10

Ecological relationship between pathogen and host can yield beneficial and detrimental outcomes.

spectrum ranges from obligate parasites (require host) to free living organisms (only feed on dead material)

Question 11

Describe the middle of the pathogen continuum spectrum.

Answer 11

facultative saprohes represent the middle of the pathogen continuum.

they are microbial organisms that are capable of surviving on dead organic matter, but also capable of attacking living host when available.

Question 12

What part of the tree will you find the following diseases symptoms.

1. Cankers.
2. Chlorosis.
3. galls.
4. dieback.
5. Conks.

Answer 12

1. Cankers are found on the trunks of trees.
2. Chlorosis can be found in the root of a tree.
3. Galls are found in the branches of trees.
4. Dieback is found on the needles or branches of a coniferous tree.
5. Conks are found on tree trunks.

Question 13

Explain disease resistance

Answer 13

resistance ranges from susceptible to tolerant to immune.

resistance is the ability of a tree to exclude or overcome the effect of a pathogen.

Question 14

What is the disease triangle?

Answer 14

relationship of pathogen with environment with host resulting in an amount of disease.
Pathogen: virulence , abundance, etc.
Environment: total conditions favoring disease
Host: conditions favoring susceptibility.

Question 15

How does the disease triangle useful in terms of disease management?

Answer 15

Elimination of 1 factor of the disease stops disease development.