Diagnosing the Causes of Plant Diseases

It can be difficult to determine the cause of a disease because some disease-causing entities may cause similar symptoms to other entities and affect the same physiological processes in the plant. For example, certain fungi cause a wet rot of tissue; a symptom usually associated with bacterial plant pathogens. Genetic abnormalities and mineral deficiencies in the plant frequently cause virus-like symptoms. Also, several agents, when successively or simultaneously involved, may be overrun by saprophytes. Sometimes infectious diseases may be obscured or emphasised by climatic or cultural factors.

For diagnosis, it is helpful to narrow the areas of confusion by being acquainted with the:

  • sorts of disease expected at the particular time of year or under the prevalent weather
  • common diseases of the host in question
  • sorts of troubles peculiar to the area (locale, location).

Contact your local agronomist, or to locate your nearest supplier, email your contact details and location to: shawn.rowe@sa.gov.au

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Using the above information will enable you to take a more considered and systematic approach to diagnostics and to better understand the more common diseases that are likely to be present on your farm. It is important to know what is normal and to be able to recognise the significance of signs and symptoms of the abnormal. Knowing the common symptom types, distribution and prevalence of diseases is helpful, though some caution may be required when making a diagnosis.

Disease Cycle: Stages of Development

Diagnostics Checklist