Which herbicide is described as having 20-100 days persistence?

• A. 2,4-D
• B. Bromacil
• C. Glyphosate
• D. Imazapyr

Answer: (A)

Persistence in soil is about how long a herbicide stays active after you apply it, before microbes, chemical processes, or leaching reduce it to inactive levels. A range of 20–100 days means the chemical remains effective for a few weeks to a few months, not just a few days and not years.

Among the options, 2,4-D fits this moderate persistence level. Glyphosate tends to break down quickly in soil, usually within days to a couple of weeks. Bromacil and imazapyr are generally more persistent, often lasting months to years in many soils. So the description of 20–100 days aligns best with 2,4-D. Remember that actual persistence can vary with soil type, moisture, temperature, and organic matter.