The main topic of the discussion of the professor and the author is how to protect the forests from the harmful microscopic fungus --phytophthora ramorum. The author suggest several possible methods, while the professor thinks that they are not practical.

  Firstly, denying the suggestion from the author that it would work if they can stopping the spreading of the spores, the professor argues that the reasons of it is hard to control the spores is that the spores are produced and diffused frequently,and they can spread not only by wind, but also by the waters. In this way, people have difficulty in control the spores that fell and moved by the rivers.

  Secondly,for the opinion that people can use the fungicidal chemicals to prevent the free disease, the lecturer contents that it will not be a effective way that use the fungicidal chemicals if there are millions of them,.Since the chemical need to be recovered after few months, it will be very impractical and expensive.

  Finally, the writer considers that clear-cutting will be able to use as well although cutting and burning the diseased
oaks would also involves destroy the nearby healthy vegetation. Then the professor argues strongly that this method will not be used as many of the vegetation are hard to grow back in a short time period, if they are destroyed, it  will lead to a serious damage to the natural environment.