Explanation

(a) Specimen J is maize plant with leaves showing a mosaic pattern/infection, tomato plant, showing leaf curl.

• The causative agent for this Condition is virus.

Specimen K is cassava leaf, showing leaf spot.

• The causative agent is fungus.

(b) Mode of transmission:

• For specimen J, the virus is transmitted by an aphid vector.
• For specimen K, the fungus is air- borne, water and rain splash

(c) Effects of each of the abnormalities on crops are:

Specimen J (effects):

• It results in stunted growth of plants.
• It leads to reduction in yield of plants.
• It causes reduction in the photosynthetic area of the leaf.

Control measures include:

• early planting:
• removal and burning of infected plants;
• eradication of insect vectors;
• use of resistant varieties; and 
• crop rotation

For specimen K (effects);

• It causes reduction in yield of crop or plant.
• It leads to the reduction in the rate of growth of plants.
• It also leads to reduction in the photosynthetic area of the leaves.

Control measures include:

• application of fungicides,
• use of resistant varieties,
• removal and burning of infected plants, and
• crop rotation.

(d) Other diseases of specimen K are;

• Cassava mosaic
• Cassava blight

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