Crime Scene Investigation (CSI) with Powdery Mildew Fungi

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This exercise can be used to stimulate the investigative nature of learners as they use forensic plant pathology techniques to prove the learners' innocence in a mock murder investigation. Learners examine the cleistothecia of plant leaves infected with powdery mildew disease with a compound microscope to identify the type of appendages present. The fungi are identified to genus using the appendage type and the number of asci (spore-containing sacs) inside each cleistothecium using both a written and an illustrated key. Learners compare their samples to the evidence found at the scene of the crime to prove their own innocence. Note: This lab works best in regions that experience cold weather for part of the year.

Quick Guide

Preparation Time:
30 to 45 minutes

Learning Time:
45 to 60 minutes

Estimated Materials Cost:
1 cent - $1 per group of students

Age Range:
Ages 11 - 18

Resource Types:
Activity, Experiment/Lab Activity, Lesson/Lesson Plan, Simulation


Materials List (per group of students)

  • Four empty envelopes
  • Envelopes with pressed, dried, leaf material infected with powdery mildew and covered with cleistothecia
  • Pen or marker
  • Scissors
  • Paper (for key)
  • Several black permanent markers or wax pencils
  • Dissecting microscopes
  • Compound microscopes
  • Clear tape
  • Petri dishes
  • Forceps
  • Several microscope slides
  • Water in dropper bottles
  • Case Study Sheet
  • Forensic Key and Diagrams to the Genera of Powdery Mildew Fungi


  • Life Sciences
    • Diversity of Life
      • Protists and Fungi
      • Classification
  • Mathematics
    • Data Analysis and Probability
      • Data Analysis
      • Data Collection
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations
      • Gathering Data
      • Formulating Explanations
      • Communicating Results

Informal Categories

  • Crime Science
  • Nature and Environment


To use this activity, learners need to:

  • see
  • see color
  • read
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Involves hands-on or lab activities


Components that are part of this resource:

This resource is part of:

Access Rights:

  • Free access


  • Ruhl, Gail


  • All rights reserved, The American Phytopathological Society, 2011