Question

From the following statements, find out the incorrect one

• A. Higher is the temperature, lesser will be the activity of herbicides.
• B. Chemical selectivity is true selectivity.
• C. Selectivity is relative property of herbicides.
• D. Due to more leaching, lower doses of herbicides are sufficient in light soils.

Hint:

Environmental warmth increases transpirational pull and metabolic rates in plants, directly speeding up the absorption and systemic movement of herbicides.
Therefore, herbicide activity increases under warmer conditions.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The efficacy and behavior of herbicides are strongly influenced by environmental factors, soil properties, and chemical selectivity characteristics.

Step 3: Detailed Explanation:
- Statement (A) evaluation: Higher temperatures generally increase the metabolic activity of plants, which enhances the absorption, uptake, and translocation of herbicides. Consequently, higher temperatures lead to greater (not lesser) herbicidal activity and efficacy, making this statement incorrect.
- Statement (B) evaluation: Chemical selectivity (based on physiological or biochemical differences in metabolism between crops and weeds) is considered true selectivity. This is a correct statement.
- Statement (C) evaluation: Selectivity is always relative. A selective herbicide can become non-selective if applied at excessively high doses. This is a correct statement.
- Statement (D) evaluation: In light (sandy) soils, less herbicide is adsorbed to clay and organic matter, leaving more free herbicide available. Because it leaches easily and is highly bioavailable, lower doses are required to achieve weed control. This is a correct statement.

Step 4: Final Answer:
The incorrect statement is (A).