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Agriculture for Secondary Schools
Rice tungro: This is a viral disease that severely affects rice crops, causing
stunted growth, yellowing, and reduced tillering. Infected plants develop
discoloured leaves with interveinal chlorosis, leading to poor grain formation and
significant yield loss. The disease is transmitted by green leafhoppers. Effective
strategies include planting resistant rice varieties, removing infected plants to
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limit the spread, and using insecticides or biological control methods to reduce
green leafhopper populations. Proper field sanitation and crop rotation also help
minimise the risk of infection. Figure 4.13 shows rice paddy plants affected by
Rice tungro disease.
Figure 4.13: Rice tungro disease in paddy plants
Brown spot disease: Brown spot is a disease caused by the fungus. It manifests as
small brown lesions on leaves, which gradually enlarge into circular spots, causing
leaf drying and weakening the plant’s photosynthetic ability. The management
of the disease includes proper nutrient management, particularly adequate silica
and potassium application, which strengthens the plant’s resistance against the
disease. Seed treatment with fungicides and using disease-free seeds are effective
preventive measures. Also, maintaining optimal soil fertility and field sanitation
reduces disease incidence. Figure 4.14 shows the effects of brown spot disease
on a paddy plant.
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