1. What are the main characteristics of a plant virus? How do viruses differ from fungi, bacteria, and nematodes? Are viruses alive? Explain your answer.
2. Why are all viruses obligate parasites? What other types of plant pathogens are obligate parasites?
3. Give an example of a symptom caused by viruses that is (a) distinct from and (b) similar to those caused by other types of plant pathogens. Are symptoms useful for diagnosing virus diseases of plants? Why or why not?
4. What are three ways that a plant virus can be transmitted from one plant to another in a field? What are three ways a plant virus can be transmitted from one generation of plants to the next?
5. ELISA and PCR are sensitive methods used for virus detection and disease diagnosis. How do these two methods differ? Why have they largely replaced the use of indicator plants?
6. Why is management of plant virus diseases almost always based on prevention, rather than cures?
