I study larvicidal effects of essential oils on house fly larvae in the lab. I use dipping method and put larvae into essential oils for 60 second after that put them on a plate with some feed for 24 hour then count number of live larvae. My problem is that I can not find death larvae between feeds particles. I used feed ingredients based on literature review. I tried different materials such as alfalfa, soy powder, yeast, grape syrup and barley powder. My question is that which feed is suitable for this experiment?

another question is that my essential oils dont kill all larvae in high concentration ( 1000 ppm was tested for Thymus vulgaric, lavendur officialis, neem oil lemon grass,...) larvicidal effect of this compouns were reported by many papers before.