1.  (12 pts) Define the following terms:


incompatible interaction






polyetic disease



horizontal resistance










2.  (10 pts)  Chose one of the following diseases (crown gall or angular leaf spot of cotton) and answer the questions below about its disease cycle. For 5 extra credit  points, answer both questions.


a) Where does the pathogen overwinter?



b) How is the pathogen disseminated?



c) What are the symptoms of the disease?



d) How can the disease be controlled?



e) How does the pathogen enter the plant?



3.  (10 pts)  Compare and contrast monocyclic and polycyclic diseases giving specific disease examples.  Draw appropriate disease progress curves of each type and label. 













4.  (9 pts) Using the disease pyramid, discuss the epidemiology of a specific (1)fungal disease, (2) bacterial disease, and (3) viral disease. 

















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












6.  (10 pts)  Due to your experience in this class, you have been called to look at a tomato field.  The plants have sunken dark lesions on the leaves and fruit.  Describe the steps you would take to diagnose the problem.  What type of pathogen would most likely cause the disease?  What control measures would you suggest for the next years crop?


















7.  (12 pts) Compare the dissemination and overwintering survival of Phytophthora, post harvest fungus, bacterial canker, root knot nematodes, cucumber mosaic virus, and dodder.















8.  (4 pts)  Discuss the role of wind in biotic and abiotic disease.







9.  (8 pts.) Compare and contrast plant sedentary endoparasitic nematodes with migratory ectoparasitic nematodes in the way they feed on plants.  What sorts of symptoms of disease are induced by each group of nematodes?  What measures can be used to control nematodes?











10.  (6 pts.)  Altering cropping density can be used as a management tool for plant disease.  Give an example of when high cropping density will increase disease and decrease yield and an example when it will increase yield without increasing disease and explain your answers.









11.  (5 pts.)  Choosing either damping off of chile or powdery mildew on chile, explain which factors you would measure in designing a predictive model of disease in New Mexico.









12.  (6 pts.)  Late blight of potato is currently a large problem in Russia due to fungicide resistant fungus strains.  Researchers are attempting to produce transgenic potatoes resistant to the pathogen.  What resistance systems do you think they should improve?  What types of genes would you recommend that they add?