Theory question 103
Crop Diseases(a) Discuss the root knot disease of tomato plants under the following headings: (i) causal organism; (ii) mode of transmission; (iii) two symptoms; (iv) two prevention and control measures.
(b) Describe three effects each of the following farming practices on the soil: (i) fertilizer application; (ii) clean clearing; (iii) overgrazing.
(c) Mention three agricultural uses of land.
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(a)(i) Nematodes (eelworms), Meloidogyne spp.
(ii) Infested soil, infected seedlings/transplants, water run-off, contaminated tools and farm equipment.
(iii) Any two: galls/knots/swellings on roots; stunted growth; yellowing and wilting of leaves; low yield.
(iv) Any two: crop rotation with non-host crops; resistant varieties; soil sterilisation/nematicides; uproot and burn infected plants; plant clean seedlings; fallowing.
(b)(i) Fertilizer: adds nutrients and raises fertility; some (e.g. sulphate of ammonia) make soil acidic; excess may harm soil organisms/cause salt build-up.
(ii) Clean clearing: exposes soil to erosion; destroys organic matter; raises soil temperature and moisture loss; kills soil organisms.
(iii) Overgrazing: removes plant cover, causing erosion; compacts the soil; lowers fertility; leads to desertification.
(c) Any three: crop production; livestock rearing/grazing; fish farming; forestry/agroforestry; farm buildings/farmstead; wildlife (game) reserves.
Name the nematode in (a)(i).