Saw my neighbor yesterday using Seven to spray for some web worms. I'm sure he never consulted his county extension office, because we would never recommend Seven.
I wonder about birds eating insects that have ingested stuff like Seven that kills everything. Maybe even birds if they eat such insects?
The extension office would have first asked how much damage the web worms were causing. From what I saw, they weren't doing much. Certainly, the affected trees will live through it.
If they recommended anything, they'd recommend BT or spinosad, MUCH safer to good bugs but deadly to worms.
Myself, I burn them out for any I can reach with a torch and leave the worms on the ground for the birds. Any higher up, just stay.