This investigative case module was prepared as part of a BioQUEST faculty development workshop entitled Investigative Case-based Learning Biotechnology 2003: Updating Educators for the 21st Century at Fralin Biotechnology Center, Virginia Tech in July 2003. The cases, resources, and implementation strategies were developed by participants for use with their own students. We invite you to adopt and adapt the following materials.

The BioQUEST Curriculum Consortium is committed to the reform of undergraduate biology instruction through an emphasis on engaging students in realistic scientific practices. This approach is sometimes characterized as an inquiry driven approach and is captured in BioQUEST's three P's (problem-posing, problem-solving, and peer-persuasion). As part of this workshop groups of faculty were encouraged to initiate innovative curricular projects. We are sharing these works in progress in the hope that they will stimulate further exploration, collaboration and development. Please see the following links for additional information:

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Investigative Cases
The Case: Family Trees

Carlos Silva sipped his morning coffee in the shade of the orange and grapefruit trees in the yard. He had planted one at the birth of each of his grandchildren and enjoyed seeing how much each had grown over the past eight years. Except for a few broken branches on the trees farthest from his house, all had survived another hurricane season.

Glancing down at the paper, Carlos was startled by the full-color map on the front page. His eyes moved quickly to the center of the map. With a sigh of relief, he found that his own home was clearly outside a yellow zone north of US 41 and east of NW 87th Ave.

Peeling the grapefruit he had just picked this morning, Carlos wondered if the small brown spots on the rind were a problem.

Case Author:
Margaret Waterman Southeast Missouri State University
Ethel Stanley Beloit College
Linda Weinland Edison College
Case User

Case Analysis

Questions include:
What causes disease?
How does it spread?
Which trees are being cut down?
What are the policy decisions?
Are there citrus that are resitant to this disease?
Is it important that his citrus are not being sold?
Is age an factor for susceptibility?
Are broken trees more susceptible?
What does the blight look like?

This is an introduced disease.
Citrus fruits include oranges, lemoms, grapefruit, and coumarins.
Citrus is grown in FL AZ TX AL
Trees are different ages.
Trees farthest from house are more damaged?
Wounded tree are more susceptible to disease?

Option: Include a know / need to know chart like the one below:

What do you know?
What do you need to know?

Learning Goals




Investigations and Activities

Label from a crate of clementines purchased at a Philadelphia fruit market.

Of what significance is the phrase, Not for distribution in AZ, CA, FL. LA, TX, Puerto Rico, and any other U.S. Territories?



Citrus products with labels

Students will usually obtain additional references or resources
to help answer or explore their questions.

Special Data Items

Guide to diagnosis of Citrus canker by Dean W. Gabriel, University of Florida, Gainesville

"Current Status of Citrus Canker" from USDA-APHIS

Citrus Canker: Threat to Florida Agriculture

Quarantine Maps

Citrus Canker in Florida through June 13, 2003

The Fundecitrus: A Fund for Citrus Plant Protection

Spatio-temporal progress of Citrus Canker in Southeast Florida

QUESTIONS (Good start)

Citrus Canker: The Pathogen and Its Impact

Citrus canker plant disease lesson from the APS Education Center and Plant Health Instructor

Article summary for Plant Health Progress review article, "Citrus Canker: The Pathogen and Its Impact"

Research Methods and Results

1. legend.JPG
2. mapsm.JPG
3. clementine.JPG
4. products.JPG


Student Products

Know/Need to Know Chart

Class brochure for residents on alternatives for the control of Citrus Canker

Assessment and Evaluation Plan



Course name:
Environmental Science
Likely sequence in syllabus:
Beginning: Our shared environment
Time during term:
First Week
Four days
Two lectures and lab/field experience
Students in course:
Majors and non-majors
Collaborative elements:
Group investigation
Additional notes:



Citrus Canker: Alternatives for Control (pdf)
Weinland, L., Woodruff, P., Waterman, M., and Stanley, E. D. (2003) Citrus canker: Alternatives for control. In Microbes Count! Problem Posing, Problem Solving, and Peer Persuasion in Microbiology. Jungck, J., Fass, M. F., and Stanley, E. D., (Eds.). Washington, D.C.: ASM Press.

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