From my understanding:
– pests don’t have perfect tolerance to pesticides, it’s just that some members of the species happen to be somewhat better at metabolizing the active substance found in the pesticide
– the active substance is only a small percentage of the pesticide, most of the pesticide is some kind of carrier oil and other inactive substances.
So, what prevents the manufacture of pesticides with much higher concentrations, much higher than any member of the pest species could ever metabolise? I understand that in open-air crops there might be considerations about collateral damage to bees etc, but this doesn’t explain why such high-concentration pesticides aren’t a thing in greenhouses.