(a) State each of the disease conditions observed on specimens C and D and their causative agents.
(b) Explain the mode of transmission of the diseases on each of specimens C and D. (C) State two effects of each of the diseases on specimens C and D and two control measures of each.
(d) Name two other diseases of specimen D.
Explanation
(a)(i) Specimen C is a maize plant with leaves showing a mosaic pattern/infection, tomato plant, showing leaf curl.
(ii) The causative agent for this condition is virus.
(iii) Specimen D is cassava leaf, showing leaf spot. The causative agent is fungus.
(b) Mode of transmission: For specimen C, the virus is transmitted by an aphid vector. For specimen D, the fungus is air-borne, water and rain splash
(c) Effects of each of the abnormalities on crops are: Specimen C (effects): (i) lt results in stunted growth of plants. (ii) It leads to reduction in yield of plants. (iii) It causes reduction in the photosynthetic area of the leaf.
Control measures include (i) early planting: (ii) removal and burning of infected plants (iii) eradication of insect vectors (iv) use of resistant varieties; and (v) crop rotation For specimen K
(effects) (i) lt causes reduction in yield of crop or plant. (ii) It leads to the reduction in the rate of growth of plants. (iii) It also leads to reduction in the photosynthetic area of the leaves.
Control measures include (i) application of fungicides (ii) use of resistant varieties (iii) removal and burning of infected plants, and (iv) crop rotation.
(d) Other diseases of specimen C are (i) cassava mosaic (ii) cassava blight