Question

A selective post-emergence herbicide used for weed control in rice is

• A. Pretilachlor
• B. Butachlor
• C. Bispyribac Sodium
• D. Tembotrione

Hint:

Look for the herbicide sprayed weeks after transplanting, once weeds are already visible in the rice field.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
We need a herbicide that is applied after the weeds and the rice crop have already emerged, and that kills weeds selectively without harming the rice plants.

Step 2: Key Formula or Approach:
Herbicides are timed either as pre-emergence, applied to the soil before weeds sprout, or as post-emergence, sprayed once the weeds are visible and actively growing. We match each option to its actual timing and crop label.

Step 3: Detailed Explanation:
Pretilachlor and butachlor are both chloroacetamide group herbicides used in rice, but they act as pre-emergence or early post-emergence herbicides applied within a few days of transplanting or seeding, working mainly on germinating weed seeds rather than established weeds.
Bispyribac sodium is a sulfonylurea group herbicide, sold under trade names for rice, and it is sprayed about 15 to 20 days after transplanting once grasses, sedges and broadleaf weeds are already growing in the field, making it a true selective post-emergence herbicide for rice.
Tembotrione is a post-emergence herbicide too, but it is registered for grassy and broadleaf weed control in maize, not rice.

Step 4: Final Answer:
Bispyribac sodium is the correct answer since it is the selective post-emergence herbicide actually labelled and used for standing weeds in transplanted rice.