Eustis about ever bag of ocean forest has fruit fly and larvae inside. FF knows this and puts hyposasis miles (beneficial bugs to eat fruit flies and larvae). I use a product called promis. Knocks them dead with one application. I ONLY use this (it's will stay with the plant for 30 days) at every up pot. I only up pot 2x, 1 From cloner to solo cup, then into 5 gal pot. I've yet to see more than 1 fruit fly, then none after the 5gal up potting.
15ml/gal for up potting to 5 gal pots, 5ml/gal for solo cup up potting. Any.more and it burns my clones a bit, but always recover.
And anything made by Bayer is the first n devil. Your supporting monsanto.