EPWS 310 FINAL EXAM, Fall 2014
1. (2 pts each) Define the following:
2. (12 pts) Chose one of the following diseases (potato scab or fireblight) 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?
f) What is the genus of the pathogen
3. (10 pts) Draw and label disease progress curves for monocyclic and polycyclic diseases. Name a disease that would be expected to show each type of curve.
4. (12 pts) Using all the components of the disease pyramid, discuss the epidemiology of a specific (1) fungal disease, (2) bacterial disease, (3) viral disease, and (4) nematode disease.
5. (5 pts) Give specific examples of how an environmental factor can cause abiotic disease and how plant nutrition can cause abiotic disease.
6. (5 pts) Migratory ectoparasitic nematodes can cause severe problems on a wide range of hosts such as corn and turf. 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 infestans which causes late blight of potato, (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 local young walnut planting. The grower noticed yellowing and dieback which is getting progressively worse and found some insect holes in the bark. 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 yearŐs crop?
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 for eastern New Mexico and why. For 3 pts extra credit, answer both questions.
11. (6 pts) Citrus greening disease (huanglongbing or HLB) is one of the largest problems in plant pathology. It is caused by Candidatus Liberibacter asiaticius (a non culturable bacteria) that is vectored by psyllid insects. You have been granted money from the US Department of Agriculture to develop plant resistance (transgenic or conventional). Explain which plant part or component or pathway of the resistance system you will try to improve. What types of genes will you modify or add to the plants?