Talstar Professional Insecticide Review | INSECT COP
May 13, 2020·For treating indoor spaces, you should mix 0.5 fl. oz. of insecticide with 1 gallon of water (14.8 ml per 3.75 liters). But for really bad infestations, you can try mixing 1 fl. oz. of the insecticide per gallon of water (29.5 ml per 3.75 liters). Do not dilute more than 1.0 fl. oz. to 1 gallon.