State two symptoms and two control measures of the following plant diseases: (a) cassava mosaic; (b) groundnut rosettes; (c) root-knot of okra; (d) bacteria...

Answer Details

(a) Cassava mosaic:

Symptoms:

1. Yellowing and mottling of leaves.
2. Stunted growth of the plant.

Control measures:

1. Use virus-free planting materials.
2. Remove and destroy infected plants.

(b) Groundnut rosette:

Symptoms:

1. Stunting of the plant.
2. Formation of rosettes, which are clusters of small, distorted leaves.

Control measures:

1. Plant resistant varieties.
2. Control aphid vectors, which can transmit the virus that causes the disease.

(c) Root-knot of okra:

Symptoms:

1. Galls or knots on the roots of the plant.
2. Yellowing and wilting of leaves.

Control measures:

1. Plant resistant varieties.
2. Rotate crops and use crop rotation practices.

(d) Bacterial blight of cotton:

Symptoms:

1. Water-soaked spots on leaves and stems.
2. Necrosis or death of infected plant tissues.

Control measures:

1. Use disease-free planting materials.
2. Apply copper-based fungicides to infected plants.

In summary, plant diseases such as cassava mosaic, groundnut rosettes, root-knot of okra, and bacterial blight of cotton can cause significant damage to crops. However, control measures such as the use of disease-free planting materials, plant rotation, and the use of resistant varieties, as well as the removal and destruction of infected plants, can help to manage and control the spread of these diseases.