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





polyetic disease






compatible interaction






disease severity









2.     (5 pts)  Give specific examples of how an environmental factor can cause abiotic disease and how plant nutrition can cause abiotic disease.







3.    (6 pts)  Sanitation steps suchas remvoing crop residue and cleaning tools can be used to manage plant diseases.  Give a disease example when sanitation will limit disease and an example when it will not decrease disease.








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 disease 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 leaf spots such as Septoria, (3) an Erwinia causing soft rot, (4) root knot nematode, (5) zucchini yellow mosaic potyvirus, and (6) dwarf mistletoe.











9.  (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?










10  (10 pts)  Due to your experience in this class you have been called to look at the NMSU golf course.  The manager tells you that he noticed circular dead areas on two of the greens. 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?














11. (6 pts)  Zebra chip disease of potatoes and citrus greening disease are two of the largest problems in plant pathology.  Both are caused by Candidatus asiaticius (non culturable bacteria) that are vectored by psyllid insects.  You have been granted money from the US Department of Agriculture to develop plant resistance (transgenic or conventional).  Choosing one of these two diseases, 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?