Theory question 105
Crop DiseasesState two symptoms and two control measures of the following plant diseases:
(a) cassava mosaic
(b) groundnut rosettes
(c) root-knot of okra
(d) bacterial blight of cotton.
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(a) Cassava mosaic (virus, whitefly): yellow-green mottling/mosaic on leaves, leaf distortion, stunting; control – resistant varieties, disease-free cuttings, uproot and burn infected plants
(b) Groundnut rosette (virus, aphid): stunted bushy plants, small yellow or mottled leaves crowded in a rosette; control – early planting, close spacing, resistant varieties, control aphids with insecticide, rogue infected plants
(c) Root-knot of okra (nematode): swellings/galls on roots, wilting, stunting, yellowing; control – crop rotation, nematicides, soil fumigation, resistant varieties, fallowing
(d) Bacterial blight of cotton (black arm): angular water-soaked leaf spots, black lesions on stems (black arm), boll rot; control – resistant varieties, seed dressing/acid delinting, crop rotation, burning debris
Two symptoms and two controls for each disease.