I hold all wc insects overnight and dont feed them off for about 24hrs. Theres no way to be 100% about them being pesticide free, but if you wait 24hrs most insects will show signs or be dead. Personally I collect from 2 areas and only those two areas because Ive used them both for 3 yrs. Imho its worth the risk to feed wc hoppers & katydids, the occas moth or dragonfly because of the benefits Ive seen in my collection.