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An Introduction To Plant Disease

Elvis Elvis

Plant disease is a detailed and multi-faceted topic. The purpose of this introduction is not to get too deep into the specifics but to touch on the basics for a fundamental understanding of plant disease.

Basically, a plant disease is any abnormal condition that damages a plant and reduces it productivity in ornamental / cosmetic look or useful to people like with vegetables for example. There are 2 basic types of Plant Disease:

  • Infectious Plant Disease
  • Non-Infectious Plant Disease

Infectious Plant Disease

Infectious plant diseases are caused by organisms that attack plants and subsequently get their nutrition from that plant. The plant then becomes the “Host Plant” and the organism causing the problem disease is called the “Pathogen”. A few common plant pathogens include the following:

* Fungi Spread by spores

* Bacteria – Examples include bacterial blight & ring rot

* Viruses – 1,000 times smaller than the tiniest living cell

* Phytoplasma – Transmitted by leafhoppers

* Nematodes – Tiny roundworms

Non-Infectious Plant Diseases

An Introduction To Plant Disease

Non-infectious plant diseases are caused an environmental factor that in turn produces an abnormal plant. Note: These types of plant diseases are NOT caused by living organisms. Some of the more Non-Infectious plant diseases include the following:

* Nutrition – Either too much or too little can cause issues.

* Moisture – Excessive or lack of water can cause issues

* Temperatures – Extremes of heat or cold can cause issues

* Toxic Chemicals – There are many examples possible here including too much road salt running off into your landscape.

Basically, there are 3 things that must be present to form infectious plant disease.

  1. The Host
  2. The Pathogen
  3. The environment

If all the “Right” conditions exist there is the chance for disease to develop and if one of the 3 are missing infectious plant disease probably won’t occur. The primary methods infectious plant disease is spread are by:

  • Insects
  • Animals & Birds
  • Water carrying with rain
  • People

Management of Plant Diseases

Non-Infectious diseases are more cut-and-dry in their management. You either add or subtract from a deficiency or excess. Infectious plant diseases are more complicated and require greater actions to correct. The 4 basic methods of infection plant disease management are:

  1. Exclusion
  2. Eradication
  3. Host Resistance
  4. Protection

There are 2 types of fungicides used to help protect against disease. (1) Protectant Fungicides work on a plants surface and (2) Systemic Fungicides are taken up by the plant tissues to help in plant disease management.

Special Note: All pesticides are poisons and should be used with extra care. Always error on the side of caution and don’t hesitate to call one of these very important organizations with questions (They are there to help and will do so very openly and expertly):

  • Local County Extension Agents
  • Local Master Gardeners

The wonder and fulfillment of growing things far outweighs the potential of plant disease. Remember, there are always reasons for the disease and subsequently courses of action to manage those plant diseases.