Radio Scripts
Package 45, Script 8
July 1997
Understanding Plant Diseases, Part One
Do you wonder why the leaves on your plants are curling up or falling off? Or why, for example, the grain doesn't form on your rice plants? There are many possible reasons. But here's one explanation. Your plants might have a disease.
Today, we will talk about what diseases are, and why plants get diseases.
What does a disease look like?
First, we will explain a little about what a disease looks like.
When a person gets a disease, many things can happen. For example, they might get a fever, cough a lot and feel hot. Their skin might turn red or feel damp. Perhaps they will feel weak and tired. And it's the same with plants!
When plants have a disease, they look and feel different too. For example, the leaves on a plant might turn different colours. Or the stem could rot and fall over. If a plant gets a disease, its fruit might get soft and rotten. Or maybe its roots will rot or swell up.
How do plants get diseases?
Plants get diseases in very similar ways to human beings. Many human diseases are caused by very tiny living creatures. We will call these creatures "disease organisms." Some disease organisms enter the human body and infect it with a particular disease. Other disease organisms can also enter plants and infect them with diseases.
There are four major types of disease organisms which cause plant disease.
They are: fungi, bacteria, viruses, and nematodes.
These disease organisms are usually carried from one plant to another by insects or by the wind.
Disease organisms need several things in order to grow and breed. They need plants to feed on, they need a certain temperature, and they need the right amount of moisture.
Many disease organisms are most active and infect more crops when their surroundings are warm and damp.
Plants are like people in another way, too.
People need good food and water to grow strong. So do plants. If your soil has lots of nutrients, and your plants have enough water, they will grow strong. If they are strong, they can resist disease better. This means that even though there may be disease in the fields or in the soil, your plants will have a better chance of staying healthy and strong.
Note
To the broadcaster: This script is the first part of a two-part series on understanding plant diseases.
Part two (Package 45, script No. 9) discusses easy, practical steps farmers can take to reduce plant disease.
Your listeners' understanding will be more complete if the two scripts are used together.
Acknowledgements
- This script was written by Vijay Cuddeford, researcher/writer, Developing Countries Farm Radio Network, and student of sustainable agriculture at the University of Waterloo, Ontario, Canada.
- It was reviewed by Dr. Darrell Cox, Ecological Concerns for Hunger Organization, Fort Myers, Florida.
Information sources
- "Fruit and Vegetable Soft Rot", DCFRN Package 8, script No. 2.
- "Developing a disease free garden", in Agriculture in action, March 1990, pages 19-20. Barbados Agricultural Society, 'The Grotto', Beckles Road, St. Michael, Barbados, West Indies.
- "How to avoid plant diseases", in Food gardens unlimited, No.79, Summer '95, pages 2-3. Food Gardens Foundation, P.O. Box 41250, Craighall, Johannesburg, 2024, South Africa.
- "Rural farmers explore causes of plant disease", by Stephen Sherwood & Jeffery Bentley, ILEIA Newsletter, March '95, Vol. 11:1, pages 20-22. Information Centre for Low-External-Input and Sustainable Agriculture (ILEIA), Kastanjelaan 5, P.O. Box 64, NL.3830 AB Leusden, The Netherlands.
- "Non-chemical methods to reduce disease infection on vegetables", Insect and Disease Control in the Home Garden, No. 64, 1979-80, 2 pages. Ontario Ministry of Food, 1 Stone Road West, Guelph, Ontario, Canada. N1G 4Y2.
- Plant pathology, by George N. Agrios, 1978. Academic Press, New York, U.S.A.
- What's wrong with my plants? A guide to identifying plant diseases caused by pathogens by Rebecca de Guzman, 1987, 19 pages. International Rice Research Institute, P.O. Box 933, Manila 1099, Philippines.
