Name   ______________________


            EPWS 310    EXAM 3    Fall 2006                     


1.    (2 pts each) Briefly define the following terms:





persistently propagative



vascular wilt















(2 pts extra credit)  clamp connection




2.    (8 pts) List the genus of a fungus that causes anthracnose.  Describe how the pathogen overwinters, how it is disseminated, and how the disease can be managed.











3.    (9 pts) List the genera of three fungi that cause postharvest diseases, describe how these pathogens overwinter, how they are disseminated, and how the diseases can be managed.










4.    (6pts) Give an example of a fungal disease where removing in the infected crop and crop residue works well to limit disease and another example where it does not work well and explain your answers.








5.    (8 pts) List the steps for a +ssRNA plant virus to replicate beginning with entry into a cell and concluding with exit from a cell.  What steps differ if the virus is (-) ssRNA?













6.    (8 pts) Explain the life cycle of corn smut.  Include how it overwinters, the spore type(s) it produces, how it infects, and how it causes disease.








7.    (15 pts) For 3 viruses in different groups, explain what types of symptoms they cause, what hosts they typically infect, how they are transmitted (vector and persistence), and how they can be controlled.












8.    (9 pts)  Diagram the disease/life cycle of wheat rust, indicating which spore stages are found on which hosts.  (For 7 extra credit points give the nuclear state (ploidy) of all stages.)















9.    (8 pts) Answer the questions below about the disease cycle of ergot.  (For 4 extra credit points, answer the questions for apple scab.)


a) What is the survival structure?



b) What serves as secondary inoculum?



c) What are the primary means of control?



d) What pathogen causes the disease


10.  (15 pts)  For each of the following methods explain the type of situation (transmission characteristics, vectors, crops etc) in which it would work (+) and not work (-) as an effective way to manage viral disease spread


a.  systemic insecticide

b.  heat treatment of tissue

c.  sanitation of tools

d.  transgenic crop plants resistant to a virus

e.  crop free period