Question

Identify the natural pest control method to prevent Tungro virus disease in paddy.

• A. Spraying insecticides
• B. Encouraging the growth of predators
• C. Using organic manures
• D. Growing blackgram and groundnut after paddy cultivation

Hint:

Tungro disease in paddy is caused by a virus transmitted by green leafhoppers. The key natural (non-chemical) control method is crop rotation with legumes like blackgram and groundnut after rice harvest. This disrupts the leafhopper life cycle by removing the rice host plant. Legume rotation also enriches the soil with nitrogen --- a double benefit.

Answer 1

The Correct Option is D

Concept:

Tungro disease is one of the most destructive diseases of rice (paddy). It is caused by a combination of two viruses:

• Rice tungro bacilliform virus (RTBV)

• Rice tungro spherical virus (RTSV)
These viruses are transmitted by green leafhopper insects (primarily Nephotettix virescens). The disease causes stunted growth, yellowing of leaves, and drastic reduction in grain yield.

Step 1: Why is crop rotation (option D) the natural pest control method?
The recommended natural method to control Tungro virus is

crop rotation --- specifically growing

blackgram (Vigna mungo) and

groundnut (Arachis hypogaea) after paddy (rice) cultivation. The rationale is:

• The leafhopper vectors that transmit Tungro virus are host-specific to rice.

• When non-host crops (legumes like blackgram and groundnut) are grown after rice, the leafhopper population collapses due to lack of food and suitable breeding ground.

• This

breaks the disease cycle naturally, without using chemicals.

• Legumes also fix atmospheric nitrogen, improving soil fertility for the next rice crop (bonus benefit).

Step 2: Why the other options are not the best natural method?

• (A) Spraying insecticides: This is a chemical method, not a natural pest control method. The question specifically asks for a

natural method.

• (B) Encouraging growth of predators: This is a form of biological control and is a natural method. However, for Tungro specifically, the primary recommended natural control is crop rotation. Predatory insects control leafhopper populations but do not eliminate Tungro as effectively as crop rotation.

• (C) Using organic manures: Organic manures improve soil health but do not directly control the virus-transmitting leafhopper vectors. This is a nutrition strategy, not a pest control strategy.

Step 3: Summary of Tungro management.
The most effective and natural means of Tungro control is through:

• Planting resistant rice varieties.

• Crop rotation with non-host legume crops (blackgram, groundnut).

• Synchronized sowing to avoid leafhopper population peaks.

• Removal of infected plants.