1.    (2 pts each)  Define the following terms:





polyetic disease






compatible interaction






disease severity






dwarf mistletoe



2.     (6 pts)  Give specific examples of how an environmental factor can cause abiotic disease and how plant nutrition can cause abiotic disease.







3.    (6 pts)  Altering cropping density can be used to manage plant diseases of annual crops.  Give a disease example when decreasing cropping density will limit disease and an example when it will not decrease disease of an annual crop.







4.     (12 pts)  Chose one of the following bacterial diseases (fireblight and bacterial cancer of stone fruit) and answer the questions below about its disease cycle.  For 6 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?



f)  What is the genus of the pathogen?




5.    (10 pts)  Draw and label disease progress curves for polycyclic and monocyclic diseases.  Name a disease that would show each type of curve.







6.    (6 pts)  Choosing either Fusarium bulb rot of onion or Stemphilium leaf spot of alfalfa, explain which factors you would chose in designing a predictive model of disease for northern New Mexico and why.  For 3 pts extra credit answer for both diseases. (Hint:  Stemphilium is closely related to Alternaria)








7.     (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.















8.  (12 pts)  Compare the dissemination and overwintering survival of  (1) Pythium, (2) a fungus causing anthracnose such as Colletotrichum, (3) an Erwinia causing soft rot, (4) corn smut fungus, (5) zucchini yellow mosaic potyvirus, and (6) dodder.











9.  (5 pts)  a) Sedentary endoparasitic 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 the cause?










10  (10 pts)  Due to your experience in this class you have been emailed to look at a peanut field in Clovis.  The grower describes the affected field as patches of wilted or dead plants.  He also write that he saw white thread-like stuff on the ground around the affected plants. Describe the steps you will take to diagnose the problem.  What type of pathogen would most likely cause the disease?  What control measures would you suggest for the next yearŐs crop?














11. (5 pts)  Sudden oak death and Pierces Disease are two of the largest problems in plant pathology.  You have been granted money from the US Department of Agriculture to develop transgenic resistance.  Choosing one of these two diseases, explain which component or pathway of the resistance system you will try to improve.  What types of genes will you modify or add to the plants?