Associate Certified Entomologist (ACE) Practice Exam

What is the primary effect of diatomaceous earth on insects?

1. It interferes with their biochemical functions

2. It causes physical injury to their exoskeleton

3. It expels moisture from their bodies

4. It enhances their waterproofing ability

The correct answer is: It causes physical injury to their exoskeleton

Diatomaceous earth is primarily effective against insects due to its abrasive properties that cause physical injury to their exoskeleton. Composed of tiny, fossilized algae known as diatoms, this substance has sharp edges that can scratch and penetrate the exoskeletons of insects. When insects come into contact with diatomaceous earth, it damages their protective outer layer, leading to dehydration and eventual death. This physical action is the key mechanism through which diatomaceous earth exerts its pest control efficacy, rather than altering their biochemical functions, expelling moisture directly, or enhancing waterproofing abilities. Consequently, the primary basis of its effectiveness lies in the physical injury it inflicts on insect bodies rather than through chemical means.