Volume 8 - How to recognize plant disorders caused by non-biological agents: A guidebook
Most forest tree seedlings are reared in nurseries before outplanting in the field. This is to produce healthy seedlings with compact fibrous roots and vigorous leaves that can withstand adverse conditions when transplanted.
There are many practices done in the nursery. For example, seeds are treated or given appropriate treatments, i.e., scarification, chilling, boiling, etc., before sowing on prepared seedboxes/seedbeds. After a few weeks, seedlings are transplanted to individual pots and watered when necessary. Organic and inorganic fertilizers are applied after root establishment. Occasional weeding is done to devoid the plants of competition for soil nutrient. When grown on large scale, irrigation is practiced to enhance the effectiveness of fertilizers and herbicides that require moist soil. When insects and/or diseases are present, usually the seedlings are immediately sprayed with insecticides/fungicides with the hope of eliminating the pest/disease. The nursery man does this often as he thinks it is necessary.
Despite rigorous care, plants still suffer from many disorders due to diseases caused by either nonbiological or biological factors. In many instances, these practices are the same factors that lead to plant abnormalities, which are noninfectious, especially when the nurseryman is careless or does not have sufficient knowledge on the occurrence and causal factors of noninfectious diseases.
This handbook, therefore, serves as a guide for nurserymen in the proper identification and diagnoses of the causal factors of noninfectious diseases of seedlings in the nursery or young outplanted seedlings from where appropriate control and/or preventive measures against these diseases could be based.


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