EPWS 310 FINAL EXAM, FALL 2003

1. (14 pts) Define the following terms:

hypersensitive reaction

disease severity

obligate parasite

compatible interaction

phytoplasma

vertical resistance

damping off

2. (10 pts) Draw and label disease progress curves for polycyclic and monocyclic diseases. Name a disease that would show each type of curve.

3. (6 pts) Explain how plant nutrition influences biotic and abiotic diseases and give examples.

4. (10 pts) Chose one of the following bacterial diseases (Clavibacter michiganense ssp. sepedonicus on potato or Streptomyces scabies on potato) and answer the questions below about its disease cycle. For 5 extra credit points, answer both questions.

a) What are the symptoms of the disease?

b) How does the pathogen enter the plant?

c) How is the pathogen disseminated?

d) Where does the pathogen overwinter?

e) How can the pathogen be controlled?

5. (12 pts) Using the disease pyramid, discuss the epidemiology of a specific (1) fungal disease, (2) bacterial disease, (3) viral disease, and (4) nematode disease.

6. (6 pts) Plowing under crop residue can be a useful method for managing plant disease. Give a disease example when this method will work well and an example when it will not help control disease.

7. (10 pts) Due to your experience in this class, a grower calls you to look at their greenhouse. The grower explains that the flowers and leaves die and then the plants die. They report that there is fuzzy stuff on the flowers. Describe the steps you will take to diagnose the problem and then prove what is causing the disease. That type of pathogen would most likely cause the disease? What control measures would you recommend for the next crop?

8. (12 pts) Compare the dissemination and overwintering survival of Phytophthora infestans, a root rotting fungus (not an Oomycete), Erwinia soft rot bacteria, corn smut, lettuce mosaic potyvirus, and dodder.

9. (5 pts) Choosing either Verticillium wilt of cotton or southern corn leaf blight, explain which factors you would chose in designing a predictive model of disease and why. For 3 pts extra credit answer for both diseases.

10. (5 pts) Lists the benefits and problems with using a transgenic plant containing a portion of a plant virus gene to control virus diseases.

11. (5 pts) a) Migratory endoparasitic nematodes can cause severe problems on hosts such as peanut. How do they interact with the plant? What sorts of symptoms do the cause?

(5 pts) b) With money from peanut growers to develop resistance to this type of nematode, what host resistance systens would you try to improve?