Question

Which among the following insect can survive at less than 2% stored grain moisture?

• A. Cadra cautella
• B. Rhyzopertha dominica
• C. Trogoderma granarium
• D. Sitotroga cerealella

Hint:

The Khapra beetle (Trogoderma granarium) is a quarantine pest famous for surviving extreme dryness ($<$ 2% moisture) and high temperatures.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Moisture content of stored grain is one of the most critical factors regulating the survival, reproduction, and metabolic rate of stored product insects.
Most storage pests require a minimum grain moisture level of 8% to 10% to survive and multiply.

Step 2: Detailed Explanation:
Let us compare the environmental tolerances of the given storage pests:
Cadra cautella (Almond moth) and Sitotroga cerealella (Angoumois grain moth) are delicate lepidopteran pests that are highly sensitive to low humidity and require moderate moisture levels to complete their development.
Rhyzopertha dominica (Lesser grain borer) is a destructive beetle, but its survival drops significantly if grain moisture falls below 8%.
The Khapra beetle, Trogoderma granarium (Coleoptera: Dermestidae), is recognized globally as one of the most destructive and resilient stored grain pests.
It is highly adapted to extremely dry and hot conditions.
Its larvae can undergo a state of facultative diapause when conditions are unfavorable, surviving without food for years.
Physiologically, Khapra beetle larvae can thrive and complete their life cycle in grains containing less than 2% moisture.
This unique adaptation is due to their highly efficient metabolic water production and minimal transpiration losses through their thick, hairy cuticle.

Step 3: Final Answer:
The insect that can survive at less than 2% stored grain moisture is Trogoderma granarium.