Question

In India, herbicide resistance was first reported in _______.

• A. Echinochloa colona
• B. Phalaris minor
• C. Ageratum houstonianum
• D. Chenopodium album

Hint:

Think of the wheat belt of Punjab and Haryana, where isoproturon stopped killing a grassy weed after years of use.

Answer 1

The Correct Option is B

This question checks awareness of the history of herbicide resistance management in Indian farming, a topic that comes up often in weed science.

1. Echinochloa colona: A troublesome grass weed of rice and other crops, but it is not the species tied to the first Indian resistance case.
2. Phalaris minor: This wheat field grass weed stopped responding to isoproturon after years of repeated use in Punjab and Haryana during the early 1990s. Field surveys and lab tests confirmed resistant biotypes, making it the first reported case in India.
3. Ageratum houstonianum: A weed of gardens and waste areas, not connected with this landmark case.
4. Chenopodium album: A common broadleaf weed of rabi crops, but again not the species involved in the first confirmed case.

The correct answer is Phalaris minor, since repeated isoproturon spraying in wheat selected for resistant biotypes that were first confirmed in India.

Let's summarize:

• Herbicide resistance builds up from repeated use of the same herbicide mode of action.
• Phalaris minor in wheat was the first weed in India confirmed resistant to a herbicide (isoproturon).

So the correct option is Phalaris minor.