I should also mention, that no matter how hard I've tried... and God knows I've tried... I too have been battling common greenhouse garden pests... The last contestants in the ring are fungus gnats... So here's what I've done...
Thirteen plants got a Beneficial Nematode / Soil top dressing which used up about 7 million BNs... It's too early to tell what I'm seeing but some radical things happened after I did this. The initial subjects, three very mature plants in flower went from sluggish liquid consumption fast paced comsumption... I know this because I chart how much they drink with the aid of sensors... This aside, it seemed that this might be the BNs killing the larvae who'd been busy munching on roots. The the pick-up in intake... Much like what happens after I Sledgehammer a plant.
As it takes time for the life cycle to end, I won't know if this licks it for a little while. In the meantime I monitor the population with yellow/blue sticky cards... (yellow for gnats, blue for thrips) ugh... I hate even saying those words...
According to all sources... this should lick the problem... I'll be sure to share my results... RS
P.S. Assuming this works. I'll make this SOP from spring to fall.... Mixing in BNs with every new pot I commission.