Name _____________________

EPWS 310 FINAL EXAM, Fall 2006

1. (2 pts each) Define the following:

horizontal resistance

conidia

phytoalexins

saprophyte

disease incidence

zygospore

damping off

broom rape

2. (10 pts) Chose one of the following diseases (Streptomyces scabies on potato or Erwinia caratovora on potato) and answer the questions below about its disease cycle. For 5 extra credit points, answer for both diseases.

a) Where does the pathogen overwinter?

b) How is the pathogen disseminated?

c) What are the symptoms of the disease?

d) How does the pathogen enter the plant?

e) How can the disease be controlled?

3. (10 pts) Draw and label disease progress curves for monocyclic and polycyclic diseases. For each curve type, name a disease that would be expected to show that type.

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

5. (8 pts) Environmental factors influence disease caused by pathogens. Give examples of how temperature (a) high and (b) low influence disease, and how moisture (a) high and (b) low influence disease.

6. (5 pts) Migratory endoparasitic nematodes can cause severe problems on hosts such as peanut. How do they interact with the plant? What sorts of symptoms do they cause?

7. (12 pts) Compare the dissemination and overwintering survival of (1) Phytophthora capsici on pepper, (2) a canker-causing fungus such as Nectria, (3) crown gall bacteria, (4) Botrytis on strawberries, (5) tobacco mosaic virus, and (6) dwarf mistletoe.

8. (10 pts) Due to your experience in this class, you have been called to look at a chile field in Rincon. At one end of the field, the plants are small and yellow, and there are lots of missing plants. The other end of the field looks pretty good. The field is on drip irrigation and looks well watered. Describe the steps you will take to diagnose the problem. What type of pathogen would most likely cause the disease? What control measures will you recommend for the next year’s crop in the same field?

9. (6 pts) Plowing under crop residue can be a useful method for managing disease. Give a disease example when this method will work well and an example when it will not help to control disease.

10. (6 pts) Choosing either Verticillium wilt of chile or stem rust of wheat, explain which factors you would chose in designing a predictive model of disease and why. For 3 pts extra credit, answer both questions.

11. (5) Against what plant disease would you recommend a genetic engineering company develop transgenic plant resistance? Explain your choice.