Theory question 105
Crop Diseases(a) Discuss briefly the rosette disease of groundnut under the following headings: (i) causal organism; (ii) symptoms; (iii) method of transmission; (iv) damage done; (v) preventive and control measures.
(b) Assuming the spacing of a vegetable crop per stand is 30 cm x 30 cm, calculate the plant population expected in a portion of land measuring 60 m x 30 m.
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(a)(i) A virus (groundnut rosette virus)
(ii) Stunted bushy plants, short internodes, small crowded leaves forming a rosette, yellowing (chlorotic) or dark green mottled leaves
(iii) Spread by aphids (Aphis craccivora)
(iv) Stunting, few or no pods, large yield loss, death of young plants
(v) Early planting; close spacing; resistant varieties; control aphids with insecticides; uproot and burn infected plants; crop rotation
(b) Area = 60 m × 30 m = 1800 m²; area per plant = 0.3 m × 0.3 m = 0.09 m²; population = 1800 ÷ 0.09 = 20,000 plants
Show the working: change cm to m before dividing.