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





horizontal resistance






incompatible interaction






disease incidence



loose smut



2.      (6 pts)  Altering cropping density can be used to manage plant diseases of annual crops.  Give a disease example when crop rotation will work well and an example when it will not help control a disease of an annual crop.






3.     (10 pts)  Draw and label disease progress curves for polycyclic and monocyclic diseases.  Name a disease that would show each type of curve.










4.     (8 pts)  Environmental factors influence disease caused by pathogens.  Give examples of how temperature (a) high temperature and (b) low temperature influence disease, and how moisture (a) high moisture and (b) low moisture influence disease.









5.     (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.













6.      (12 pts)  Chose one of the following bacterial diseases (angular leaf spot of cotton or ring rot of potato) 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?


7.      (5 pts)  a) Sedentary endoparasitic nematodes can cause severe problems on a wide range of hosts such as tomatoes and soybeans.  How do they interact with the plant? What sorts of symptoms do they cause?








8.      (6 pts)  Choosing either Alternaria leaf spot of tomato or Fusarium wilt of tomato, 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.










9.      (12 pts)  Compare the dissemination and overwintering survival of  (1) Phytophthora ramorum which causes sudden oak death, (2) Rhizopus causing soft rot, (3) crown gall bacteria, (4) corn smut fungus, (5) alfalfa mosaic virus, and (6) leafy mistletoe.






















10  (10 pts)  Due to your experience in this class, you have been called to look at small pistachio trees in Alamogordo. This new grower tells you that a newer block of trees is declining and has stunted trees with small galls on the upper stems, and leaves growing in clumps. The roots appeared to be somewhat gnarled, but were not discolored and the plants were well watered.  Almost every plant has the odd symptoms.  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. (5 pts)  Phytophthoa ramorum,which causes sudden oak death, is one of the most important disease problems in currently in plant pathology.  You are writing a grant for funds to develop resistance (transgenic or conventional) to the disease in coastal redwoods, which are completely susceptible to the fungus.  What component or pathway will you try to improve?  What types of genes will you modify or add to the plant?