Question

Which of the following herbicides is highly volatile?

• A. Pendimethalin
• B. Atrazine
• C. Ethalfluralin
• D. EPTC

Hint:

Think about which chemical group of herbicides must be mixed into the soil within minutes to avoid vapour loss.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We need to pick the herbicide known for high volatility, meaning it escapes into the air as vapour soon after it is sprayed on the soil surface.

Step 2: Key Formula or Approach:
Volatility depends on the chemical group of the herbicide. Thiocarbamate herbicides have a very high vapour pressure and are lost from the soil surface within minutes if left unincorporated, so they always need immediate mechanical mixing into the soil. Dinitroaniline herbicides like pendimethalin and ethalfluralin are also somewhat volatile and light sensitive but less so than thiocarbamates. Triazine herbicides such as atrazine have low volatility.

Step 3: Detailed Explanation:
EPTC (S-ethyl dipropylthiocarbamate) belongs to the thiocarbamate group and is one of the most volatile herbicides used in field crops. It must be incorporated into the soil within minutes of application, otherwise most of the active ingredient is lost as vapour before it can act on weed seeds.
Pendimethalin and ethalfluralin, both dinitroanilines, do need shallow incorporation or rainfall to avoid photodecomposition and some vapour loss, but their volatility is much lower than that of EPTC.
Atrazine is a triazine herbicide with very low volatility and is commonly used as a surface application without incorporation.

Step 4: Final Answer:
EPTC is the correct answer because thiocarbamate herbicides are the most volatile among common field herbicides and must be incorporated right after spraying.