>but I've come to understand that illegal growers often use toxic pesticides that further increase yield-- and thus it is important to know where your weed comes from.

A lot of illegal weed is from the same supply chain as the legal stuff, but unreported, similar to bootleg products that are sourced from the same factories as the authentic stuff.

I do agree that it's a problem not knowing where it came from, but it seems that legal weed has really raised the bar, and the street has to compete at some level. I've heard street weed is a lot higher quality now than pre-legal weed.