Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Defin by WIKIPEDIA
A.Plant environment
Plants which grow under conditions which favour healthy growth often develop a form of natural resistance to diseases and are less likely to be infected than plants which are weak and lacking in vigour due to factors such as low soil fertility, a lack of or excess water in the soil, shading from weeds or other plants or exposure to excessive sun or wind.
Cultivation measures such as good soil preparation, the addition of organic material to the soil, drainage of waterlogged soils, regular irrigation during the dry season, the use of mulches to prevent loss of water and weed competition, the provision of shading for young seedlings and planting windbreaks or shelter belts for crops exposed to strong winds, will all contribute to healthy plant growth and reduce the incidence of diseases.
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B. Resistant cultivars:
Although these are not always readily available, sowing or planting cultivars which have been found to be resistant to some diseases should be done whenever possible. This applies mainly to annual crops but some tree crops such as citrus can be budded on to Tristeza virus-resistant rootstock such as Cleopatra mandarine. Spome cultivars of cassava which are resistant to cassava mosaic virus have been produced in Research Institutes in Nigeria.
C. Use of disease-free seed and planting material:
Seeds obtained from reputable sources should be free from disease but if they were likely to be infected, they should be dressed with a fungicidal treatment which will kill any spores of fungi which may be attached to the seed coat. Cuttings or tubers should also be obtained only from healthy plants; if suspected of being from diseased plants, they should be dipped in a fungicidal solution before being planted.
D. Crop rotation
This has already been referred to in Chapter 2. The regular rotation of crops will prevent the build up in the soil of fungi and other pathogens which may have an independent stage in their lifecycle.