Maize grains are best stored against insect attacks by__________________

Step 1: Analyze the question The question asks for the best way to protect stored maize grains from insect attack (storage pests such as weevils, Sitophilus zeamais, and the larger grain borer).

Step 2: Explain the concept Stored grains are attacked by insects when they are exposed to air, moisture, warmth, and open access. Good storage methods:

• Keep grains dry (about 12-13% moisture or less)
• Seal off the grains from insects and rodents
• Reduce oxygen and control temperature
• Often treat with a storage chemical (e.g., phostoxin) or use clean, airtight containers

A silo is a large, airtight, sealed storage structure, usually made of metal or concrete. Its closed design keeps out insects, rodents, and moisture. Many silos can also be fumigated, which makes them the most effective option listed.

Step 3: Evaluate the options

• A. Keeping in a silo: Sealed, controlled, and can be fumigated. This is the best protection.
• B. Storing in the room: Open to insects, rodents, and humidity, so grains are easily infested.
• C. Leaving them on their cobs: This gives some short-term traditional protection (the husk covers the grain), but the grain is still exposed and insects can get in. It is not the best method.
• D. Covering with leaves: Leaves do not seal out insects and may even add moisture, which encourages pests and mold.

Step 4: Answer The correct option is A. keeping in a silo.

Tip: In storage questions, think "airtight, dry, and protected." If one option describes a sealed structure (silo, barn with treatment, airtight container), it is usually the best answer. Also remember common storage methods: drying, fumigation, use of insecticides, and cribs or silos.