How to prevent onion maggot in onion crop

The onion’s maggot is a very small white colored insect
It affects the onion tuber
In large tubers, 9 to 10 maggots attack and make it hollow.
Because of which the onion tubers rot completely
To prevent this pest, use Fipronil 0.3% 7.5 kg/acre or cartap hydrochloride 7.5 kg / acre as a soil treatment.
Fenpropathrin10% EC @ 400 ml/acre or Chlorpyriphos 20% EC @ 1 liter/acre.
Spraying Beauveria Bassiana @ 250 gram/acre as a biological treatment.