Plant diseases affect the existence, adequate growth and productivity of all kinds of plants. A diseased plant is a plant that cannot carry out all the physiological functions. So, the importance of plant diseases in the agriculture sector is very significant.
In the developing countries, 50-80% of the population is directly engaged in agriculture and they also have the lowest agricultural output. To feed these people the possible methods of increasing food supply should be pursued. One of these methods is to protect the crops from diseases. Some of the importance and consequences of plant diseases are shortly stated here:
- Plant diseases may limit the kinds of plants and industries in an area. Such as- Chestnut blight disease, Dutch elm disease, etc.
- Plant diseases reduce the quality & quantity of plant production. For example – it is estimated that in the USA due to the Dutch elm disease almost all the American elm trees were lost (from 1918 to present).
- Plant diseases may make the crops or plants poisonous to humans and animals, For example: Ergotism & Ergot of rye – caused by Claviceps purpurea. Mycotoxins – Aspergillus secretes Aftatoxins, which is very poisonous.
- Plant diseases may cause the financial losses; expenses of labour, chemical cost etc. For example. It is estimated that in USA, crops. worth $ 9.1 billion are lost due to diseases, every year. So this plant diseases have a very serious impact on the agriculture of a country or a locality.
- Plant diseases are even responsible for human migration. For example: The water mold, Phytophthora infestans was the causative agent of the great Irish famine (1845-1849) that caused a million of death of Irish and another million left the island before the famine lifted in 1852.
Some examples of the impact of diseases:
|Type of impact||Disease||Agent||Country or region with period|
|Famine||Late blight of potato||Phytophthora infestans||Ireland (1845-46)|
|Famine||Brown spot of rice||Drechslera oryzae||India (1942-43)|
|Economic||Coffee rust||Hemileia vastatrix||Srilanka|
|Economic||Panama disease of banana||Fusarium oxysporum||Central America (1930-55)|
|Agriculture||Southern corn leaf blight||Bipolaris maydis||USA (1970)|
|Agriculture||Citrus canker||Xanthomonas campestris var. citri||USA, South America|
|Ecological||Dutch elm diseases||Ophiostoma novo-ulmi||Northern hemisphere|