EPWS 310  EXAM 3, Fall 2001


1. (12 pts) Briefly define the following terms:

















persistent circulative



2. (8 pts) Give the genus of a fungus that causes southern corn leaf blight.  Describe how the pathogen overwinters, how it is disseminated and how it can be controlled.










3.  (8 pts) Outline the life cycle of covered smut of wheat.  Include how it overwinters, the spore types, how it infects and how it causes disease.









4. (10 pts) Basidiomycetes can cause root and stem rots of plants.  What are two fungi that cause these diseases, how can they be identified, how do they overseason, and what measures work to control them?












5.  (10 pts)  Answer the questions below about the disease cycle of apple scab.  (For 5 points extra credit, answer the questions for Armillaria root rot.)


a) What is the survival structure?



b) What serves as primary inoculum



c) What serves as secondary inoculum?



d) What is the primary means of control?



e) What pathogen causes the disease?




6. (10 pts) Describe 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?









7.  (8 pts) Give an example of a fungal disease where plowing the crop residues into the soil will work well and one where it is of limited value and explain your answers.










8.  (10 pts)  For 2 viruses in different groups, discuss what types of symptoms they cause, what are the hosts, how they are transmitted (vector and persistence), and how they can be controlled.











9.  (14 pts)  Diagram the life cycle/disease cycle of stem rust of wheat.  Show the nuclear state of all stages and which host it is on.






















10.  (10 pts) 7.  For what type of situation (transmission characteristics, vectors, crops, etc.) would each of the following methods NOT work for as an effective way to manage viral disease spread?


a.  insecticides

b.  crop free period

c.  rogueing

d.  planting virus-free seed

e.  transgenic crop plants resistant to a virus