Observation

Although many candidates displayed poor knowledge of rosette and gummosis diseases in Question 3(a), their responses in Question 3(b) and (c) were above average.

The expected answers include:

1. (a)        Completion of table on crop diseases

            Rosette disease
(i)         Crop affected
-   Groundnut

(ii)        Causal Organism
-   Rosette virus/virus                                                             

(iii)       Symptom
-   Thick, crinkled and mottled leaves
-   Curling of leaves
-   Yellowing of leaves
-    Stunting of plant

(iv)         Control measures
-   Early planting
-   Uprooting and burning of infected plants
-   Practising crop rotation
-   Close spacing
-   Use of resistant varieties
-   Spray insecticide to control the vectors/aphids

Gummosis
(i)        Crop affected
-   Citrus/orange                                                                     
(ii)        Causal organism
-   Fungus/Phytophthora parasitica                                       

(iii)       Symptom
-   Rottening of the bark near the ground
-   Drying and cracking of bark
-   Release/exudation of gum or slimy substance from the bark
-   Leaves turn yellow and begin to die back

(iv)       Control measures
-   Use of resistant varieties
-   Spray with appropriate fungicides
-   Paint the trunk with crude carbolic acid and water

(b)        Examples of Crops
(i)         Grain legumes
-   Cowpea                   -   Groundnut              -   Pigeon pea                         
-   Lima bean               -   Soya bean               -   Bambara nut
-   Broad bean              -   Lentils                    

(ii)        Spices
-   Ginger                     -   Fennel                     -   Pepper/Chili/Black pepper 
-   Onion                      -   Clove                      -   Garlic
-   Tumeric                   -   Cinnamon               -   Thyme                                            

-   Cumin                     -   Nutmeg                   -   Rosemary

   (c)        Problems associated with irrigation in West Africa
-   Irrigation equipment is expensive to install
-   Pollution of irrigation water by toxic chemicals
-   Cost of maintenance is high
-   Disturbs free movement of farm machinery
-   Inadequate technical know-how on irrigation establishment and operations
-   Inadequate water supply
-   Encourages build-up of pests
-   Encourages build-up of diseases
-   Encourages weed growth
-   Could lead to soil salinity
-   Could lead to flooding
-   Could lead to erosion
-   May cause leaching