Amount of ammonia required to control Pistia:

Correct option is A

Correct Answer: (a) 1% aqueous solution with 0.25% of wetting agent
Explanation:
→ For Pistia stratiotes control, a 1% ammonia solution (with ~0.25% surfactant/wetting agent) is an established chemical method to cause plant desiccation and death.
→ The wetting agent improves contact and penetration of the alkaline solution.
Information Booster:
→ Chemical control must be applied carefully to avoid non-target impacts and follow environmental regulations.
Additional Information (Other Options):
(b–d) Higher concentrations may be more toxic to non-target fauna and are not standard practice.