Question

………… is the most widely used fumigant for grain disinfestation in the world.

• A. Methyl bromide
• B. Hydrogen peroxide
• C. Phosphine
• D. Formaldehyde

Hint:

In India, you will see Aluminum Phosphide tablets commonly sold as "Celphos." This is the source of the Phosphine gas.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the primary gaseous chemical used globally to kill insects in stored grains.

Step 2: Detailed Explanation:

• Fumigation: This is the process of using toxic gases to penetrate bulk storage (like silos or bags) and kill pests.

• Phosphine ($PH_3$): Phosphine gas, typically generated from Aluminum Phosphide or Magnesium Phosphide pellets, is currently the most widely used fumigant in the world. It is highly effective against all life stages of stored-product insects, easy to apply, and leaves negligible residue if used correctly.

• Methyl Bromide (Option A): Historically, this was the most widely used fumigant because it acts very fast. However, it was found to be a major ozone-depleting substance and has been phased out globally under the Montreal Protocol (except for very limited "Quarantine and Pre-shipment" uses).

• Comparison: Because of the phase-out of Methyl Bromide, Phosphine has taken over as the global standard for routine grain storage.

• Other Options: Hydrogen peroxide and formaldehyde are used for surface disinfection or sterilization of equipment, not for bulk grain fumigation.

Step 3: Final Answer: Phosphine is the world's leading grain fumigant.