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Chapter 7 Instructor Resources​

Roles People Play: Epidemics and Their Management

Plant disease epidemics are often the result of human activities, as in the southern corn leaf blight epidemic of the 1970s, but can result from natural events, as in the brown spot of rice epidemic in India of the 1940s. Epidemics can be classified into categories that direct the appropriate choices of management practices. These practices include exclusion of the pathogen, eradication of the pathogen, and protection of the plant. Management practices can be incorporated into integrated pest management (IPM) programs that reduce the need for pesticides, prolong the usefulness of resistance genes, and reduce losses to diseases.

• Chapter 7 Podcast

  Chapter 7 Podcast

  Listen to the Podcast (mp3)
  

  The short podcast provided for each chapter includes a review of a major concept or issue, clarification of an important point that can be confusing to students, and questions for students to think about. This podcast discusses the difference between endemic and exotic organisms and contrasts monocyclic and polycyclic diseases and their management strategies.

• Short Writing Assignments

  Notes: These assignments requires each student to write a paragraph (introductory sentence, body, concluding sentence) and can be completed in 10–15 minutes in class. It provides a good way to check student comprehension and to improve student writing skills. See Chapter 1 for a simple grading system.

  
  

  1) Roles of People in Plant Disease Epidemics

  You have learned about plant disease epidemics and the factors that can affect their development. The actions of people have played major roles in many of the epidemics studied thus far. Describe one way people’s actions have fostered the development of plant disease epidemics and one way people’s actions have been used to suppress (manage) epidemics. Give a specific example of each using different diseases.

  
  

  2) Endemic Versus Exotic Plant Diseases

  Plant diseases can be endemic or exotic. In paragraph form, define the term endemic disease and briefly describe why endemic diseases are usually less destructive than exotic diseases. Give an example of a serious epidemic of an endemic plant disease, and describe what aspect(s) of the disease epidemic pyramid changed to allow the typically minor plant disease to develop into a serious epidemic.

  
  
• Longer Writing Assignments

  1) Garden Plan

  Plan a garden using a seed catalog. You may use catalogs you have at home or the Park Seed online seed catalog

  Go to the “Vegetable” section. Choose 10 vegetable cultivars. (That is, don’t write just “cucumber.” Pick a particular type of cucumber.) If you click on the name of a cultivar, you will see lots of information about it. Explain why you chose each (color, taste, time to maturity, disease resistance, etc.). Notice especially with tomatoes that you may choose cultivars with Verticillium wilt resistance, Fusarium wilt resistance, and root-knot nematode resistance (VFN), as well as Tobacco mosaic virus resistance. Notice also how many of the seeds are hybrids (so they will not “breed true” if you collect seeds to plant next year).

  After you have chosen 10 vegetables, research each plant to find the genus (the first word in the scientific or Latin name) and the origin of the species: Eastern Hemisphere (Africa, Asia, Europe) or Western Hemisphere (North and South America). You can find this information using an Internet search engine, such as Google.

  Make a drawing of your garden that shows where you will plant each vegetable. You should rotate sections of your garden by botanical family. Do not plant vegetables from the same family in the same area of your garden in consecutive years. It is better to plant each family in a section (perhaps one-fourth of a square or rectangular area) than in single rows to reduce spread of soilborne pathogens from one section to the next. Most rotations are planned on a 3- or 4-year basis. Using arrows, show your rotation plan according to botanical families.

  You might want to use some of the families in the following list for sections of your garden and then add a section for miscellaneous species, depending on your preferences.

  These four botanical families are commonly found in home gardens:

  • Cucurbits: cucumbers, melons, pumpkins, squash
  • Crucifers: broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, radishes, turnips
  • Legumes: beans, peas
  • Solanaceous plants: eggplant, peppers, potatoes, tomatoes

  
  

  Your completed assignment should include the following:

  1. A list of 10 vegetables:
  • The genus (scientific/Latin) name of each
  • Each vegetable’s origin (Eastern or Western Hemisphere)
  • The specific cultivars of each vegetable
  • Why you chose the vegetable and the specific cultivar
  
  
  2. A diagram of your garden, including where each vegetable (grouped by family) will be planted and a 3- or 4-year rotation plan

  
  

  Evaluation of garden plan: 30 pts.

  
  

  List of 10 vegetables, accurate scientific name of each, accurate hemisphere of origin of each	10 pts
  Explanations of vegetable and cultivar choices	10 pts
  Diagram of garden that groups plants by family and shows correct rotation plan	10 pts
  	Total: 30 pts

  
  

  Notes:

  • It’s amazing how few students have looked through a seed catalog. Many are quite surprised at all of the choices they have. They also are quite surprised at the number of cultivars with resistance to many of the diseases they have been hearing about.
  • Students are quite passionate about their tastes in vegetables. They choose different types for many interesting and amusing reasons, such as pleasing their mothers. Some students get out their colored pencils or cut and paste color images from the Internet. Each year, a few students choose some perennials, such as asparagus, strawberries, and rhubarb.
  • Although crop rotation is discussed in class, many students do not really understand the concept until they have to group their choices by family. Students seem to really enjoy this exercise and probably learn a lot more than they realize.

  
  
  

  2) Managing a "Hot" E​pidemic

  Keep an eye on the news for a “hot” plant disease epidemic: locally, nationally (e.g., late blight in 2009), or internationally (e.g., the Ug99 race of the wheat stem rust pathogen). Then write a short paper stating and supporting your opinion on the effectiveness of the current proposed/enacted management strategy for this epidemic.

  Here are some questions to consider:

  • Do you believe the strategy (e.g., quarantine, eradication, fungicide, resistant cultivars) will be successful? Why? If so, for how long?
  • Also consider the economics of the situation. Will the proposed management strategy be cost effective for producers? For consumers?

  
  

  Notes:

  • You can make the audience for the assignment someone other than yourself—for example, members of a state legislature or a consumer organization. The selected audience should dictate the style of writing students use.
  • Opinion papers such as this can be written in several drafts: Draft 1 (evaluated but not graded) summarizes the facts; draft 2 (also evaluated but not graded) incorporates the student’s opinion, supported by the facts; and draft 3 is a polished version of draft 2, which is finally graded. Students appreciate the opportunity to get feedback on their writing and thinking before being assigned a grade. This system also provides an opportunity for students to learn to separate facts from opinions and to evaluate the biases of different sources of information.
  • You can provide students with a reference list (including links), so that this is an exercise in evaluating and using information, rather than finding it. Extra credit can be given for sources with new information that students find and use in their papers.

  
  

  Evaluation of Paper:

  Criteria used in evaluation can include the following:

  • Accuracy and completeness of factual information
  • Development and support of opinion
  • Overall organization and clarity
  • Mechanics (e.g., spelling, grammar, sentence structure)
  • Use·of supporting references

  
  

  Important Note: This paper has no “right” or “wrong” conclusion. The student can take either side of the issue (pro–management strategy or anti–management strategy), include the pertinent facts, and use them to support his or her position.