(a). State three effects of maize weevil on maize grains. (b) Explain briefly five general control measures of insect pests of grains in storage. (c) Name the vector for each of the following crop diseases: (i) groundnut rosette; (ii) maize streak; (iii) cassava mosaic.
Explanation
6(a) Effects of maize weevil on maize grains are: (i) destroys the endosperm, thereby, reducing the food value grains. ( (ii) reduces viability of infested grains as the embryos are damaged. (iii) reduces market value of infested grains. (iv) predisposes infested grains to other pathogenic microorganisms attack. (v) reduces the quantity of the maize grains and produce.
(b) General control measures of insect pests of grains in storage are: (i) Early harvesting of grains such as maize, guinea corn and cowpea reduces the level of infestation and damage in the field. (ii) Proper cleaning and fumigation of sores before grains are stored helps to reduce the level of infestation and damage. (iii) Storage of maize -cobs with or without the husks and guinea corn heads over fire places where they are regularly smoked has been found to be effective in controlling the insect pests (iv) Storage and fumigation of she in silos or sealed polythene bags/ containers. (v) maize cob stored in cribs and unthreshed guinea corn heads in rhumbus should be treated with insecticides such as Actellic 25 dust or liquid, (vi) Grains should be dried to reduce their moisture content to the desired level to kill the eggs and larva of pests.
(c) Insect vectors of crop diseases are: (i) groundnut rosette - aphid (ii) maize streak - Piercing and sucking insects e.g capsid or scale insects. (iii) cassava mosaic - white fly.