The Case Background Information
This case study introduces students to differences in disease management between organic and non-organic agriculture and strengthens their understanding of the disease triangle concept. Through the lens of a grower undergoing the required three-year transition from non-organic to organic production, the case study dramatizes the challenges of combatting cucumber beetles and cucurbit bacterial wilt while producing organic muskmelons. In the case study, the grower decides to grow muskmelons in his first year of the transition process after years of successful non-organic muskmelon production. Anticipating higher production costs and a three-year waiting period before his muskmelons can be marketed as certified organic to earn a higher price, the grower took out a loan. But in the first growing season he loses most of his crop to cucumber beetles and the bacterial pathogen they vector, and learns the hard way that the organic-approved insecticides for these pests are not as effective as the conventional insecticides he relied on in prior years. Faced with the risk of defaulting on his loan, the grower must adopt pest management strategies that will more reliably manage cucumber beetles and bacterial wilt if he wants to produce organic muskmelons in the future. The case study presents several organic-approved management options – each with distinct pros and cons – and tasks students with proposing appropriate management strategies for the grower and understanding the scenarios in which each option may be appropriate.
Suggestions on how to use this case
This case study is designed for use in a single 50-minute class of 10 to 50 students. However, the case can readily be extended to longer class periods or multiple periods. The target audience is undergraduate students in plant pathology, entomology, horticulture, vegetable production, integrated pest management, sustainable agriculture, pest protection, organic agriculture, agriculture education, or related disciplines.
It is recommended that students read the case study prior to class and come to class prepared to discuss the discussion questions embedded in the case study text. A pre-class quiz can be used to help motivate students to read the case carefully, and therefore be prepared to discuss it in class. The background text should be made available to students who wish to read it for further information.
In a 50-minute class period, the instructor may use 5 to 15 minutes to summarize the content of the case study and background information as well as discuss and answer the questions embedded in the case study. For the following 20 to 30 minutes, students may be divided into small groups of 2 to 5 people to discuss and agree on a disease management plan they would propose to the grower in the case study. The remaining 10 to 15 minutes of the class period can be used for groups to present their proposals and engage in large-group discussion or debate over the pros and cons of each strategy.
During Fall Semester 2018, we tested the case study in an undergraduate-level introductory plant pathology course (PLP 408/508) at Iowa State University with a class size of approximately 45 students. In responses to a written survey evaluating their reactions to the case study, more than half of the 20 students who responded indicated that the parts of the case study that contributed most to their learning included reading the case study prior to class, in-class lecture, and the in-class group work. Several students expressed a desire to understand more about the insect vector, so dialogue between the case study's characters was modified to include more information about the vectors and to explain more clearly how managing the causal agent is dependent on managing the vectors.