Terry Stewart

Institute of Natural Resources
Massey University
Palmerston North
New Zealand


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The plant pathology-teaching tool DIAGNOSIS has been used at Massey University and other institutions for a decade.  This paper describes the value in the teaching approach it uses and it's evolution over the last 10 years. More information on DIAGNOSIS can be found at http://www.diagnosis.co.nz and in the references below.

Those unfamiliar with DIAGNOSIS should click here for a quick explanation of what the software does.  Don't let the name fool you.  DIAGNOSIS is not a diagnostic expert system.

The Educational Value of DIAGNOSIS

Educational experts generally agree that incorporating a problem-solving approach in instructional design can facilitate learning (for some good reference material on this subject see this document by educationalist David Merrill ).  DIAGNOSIS presents students with a problem to solve, captures their diagnosis, justification and solution and provides feedback.  Students generally react very positively to the exercises.  They are forced to integrate and synthesise material learned elsewhere in other courses (soil science, plant physiology, entomology etc.) thereby looking at a problem in a holistic way. In this way they learn the "art" of diagnosis (Grogan, 1981).

The exercises seem to work best when the students undertake them in pairs or small groups.  This way they can bounce ideas off each other, working and communicating as a team.

Another useful exercise is to get students to actually construct scenarios themselves, then get other students to play and critique them.  Just as having to teach material forces a new teacher to learn it well, constructing scenarios makes students think about how a plant problem may relate to management and the environment in which it exists. 

Embedding DIAGNOSIS in a course

Versions 1 and 2 of DIAGNOSIS were designed to be firmly embedded in a series of lectures on the diagnostic process.  The software is designed to complement, not replace, hands-on laboratory work.  The present version of the software does not provide reference material to assist in the diagnosis.  Students are expected to use reference material from elsewhere (books, their lecture notes, the web etc.).  However, version 3, presently being worked on (described below), will allow the embedding of reference material or links to it.

Some History: The Genesis and Evolution of DIAGNOSIS

The original DIAGNOSIS was written in 1989 in Pascal.  It was designed to be used under MS-DOS.  The software could show images and used a simple verb-noun combination for interaction.  Readers can download this old version for free here.  The relationship between this and early text-based adventure games is obvious.   The builder program was simply a compiler, which parsed a formatted scenario text file and converted this to a data file for use in the student player.

Some Menu Options in Diagnosis V 2

Figure 2. Some menu options in DIAGNOSIS V.2

In 1992, a collaboration was formed with the CAL Program in the Co-operative Research Centre for Tropical Pest Management (now the Centre for Pest Information, Technology and Transfer), The University of Queensland, Australia, to produce a Windows 3.1 version (version 2.0).  This version, Called DIAGNOSIS FOR CROP PROTECTION, used pre-set menus rather than verb-noun combinations (Fig 2).  It allowed for a range of crop types, included pest diagnostic procedures, expanded on available laboratory tasks, accommodated pest problems and allowed video to be incorporated into scenarios.  The builder was interactive and a lot more user-friendly.  A review can be read here.

Version 2.1 (the present commercial version) incorporated the ability to save the student session while in progress, to add audio and export scenarios to a text file.  The manual was also expanded to include information on how to embed DIAGNOSIS FOR CROP PROTECTION in a course.

Macintosh Diagnosis Startup Screen

Figure 3. Macintosh version of DIAGNOSIS Start-up screen

A Macintosh version was also produced in 1992 using a generic plant (Fig 3) and laboratory which students could explore with the mouse.  This version was discontinued due to the expense of supporting two different computer platforms.


Version 3.0 (almost complete) is a radical re-write, utilizing modern Windows technology and 98/NT/2000 conventions.  The product will be called DIAGNOSIS FOR CROP PROBLEMS.  It considerably enhances the DIAGNOSIS experience by allowing customisable menus and interfaces (Figs 4 and 5).  It also allows tutors to embed (or link to) reference information.  This feature enables teachers to provide not only the problem, but also information on the significance of what the student is considering at the time.

Figure 4. The Customisable Version 3 Player showing the introduction to a scenario  

Figure 5. Builder Screen Shot from Version 3.

With the previous version of DIAGNOSIS, students were not aware of the significance of observations until the de-briefing at the end.  Here, there is the option to provide feedback as they explore the scenario.  Version 3 should be available towards the end of 2001.

There are a number of issues and difficulties with maintaining and supporting teaching software within an academic framework.  The production and support of educational software for a specific narrow discipline is becoming increasingly difficult as operating systems become more complex, institutions become more commercially-minded and programmers become more expensive.  A related symposium paper explores these problems.

Final Comment

Teaching programs such as DIAGNOSIS enhance student learning.  However, like all technology, it is how it is used that matters.  The value of DIAGNOSIS as an educational experience is not the builder and the player software, useful though these are.  In fact a "Diagnosis" exercise could be done using sealed envelopes, containing photos and descriptions of facets of the scenario.  When a students wants to "examine the leaves" they could break into the envelope containing observations from this activity. Lo-Tech for sure,  but it would provide a similar learning experience.

The real value of DIAGNOSIS is in the quality of the scenarios and how the exercises are used within a course.  This quality and appropriateness of use comes from dedicated plant pathology teachers and practitioners themselves.  The experience, wisdom and knowledge of extension plant pathologists can be embodied in a scenario, and used by a skilful teacher to challenge students.  

Technology can help but it is an aid to, not a substitute for, careful curriculum planning, inspired examples and good teaching paradigms.  DIAGNOSIS is a useful tool, but it will always require good teachers to realise its full potential.  


Grogan R.G., 1981. The Science and Art of Pest and Disease Diagnosis.  Annual Review of Phytopathology 19: 333-351

Stewart T.M., 1992.  Diagnosis. A Microcomputer-based teaching-aid: Plant Disease 76: (6): 644-647

Stewart T.M., Blackshaw B.P., Duncan S., Dale M.L., Zalucki M.P. and Norton G.A., 1995.  Diagnosis: a novel, multimedia, computer-based approach to training crop protection practitioners.  Crop Protection 14: (3): 241-246.

Stewart T.M., 1997.  Computer games and other tricks to train plant pathologists.  In. Information Technology, Plant Pathology and Biodiversity (Bridge, P.D., Jeffries, P. and Morse, D.R. (eds)).  CAB INTERNATIONAL, UK


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