Wyoming Pesticide Applicator Certification Practice Test

What is the primary cause of pesticide downward movement in the soil?

1. Highly water-soluble pesticides

2. Photodegradation

3. Runoff or leaching

4. Microbial action

The correct answer is: Highly water-soluble pesticides

Highly water-soluble pesticides are the primary cause of pesticide downward movement in the soil because they are easily dissolved in water and can therefore be carried downwards through the soil layers. Photodegradation, or the breaking down of pesticides by sunlight, does not necessarily cause downward movement in the soil. Runoff or leaching can result in pesticides being carried away from the application site, but it is not the primary cause of downward movement. Microbial action, or the breaking down of pesticides by microorganisms in the soil, also does not typically lead to downward movement.